SOLUTIONS – INSIGHTS REVISION TEST for Preliminary Exam 2018: Test – 61(Environment and General science)

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SOLUTIONS 

INSIGHTS REVISION TEST for Preliminary Exam 2018: Test – 61(Environment and General science)


 

  1. Which of the statements are correct with respect to Conservation International (CI)?
    1. It is an intergovernmental Organization.
    2. Its goal is to protect nature as a source of food, fresh water, livelihoods and a stable climate.

Select the correct answer using the codes below:

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

Solution: b

Explanation:

During the inaugural session of the four-day Asia Pacific Regional Workshop of the United Nations Convention to Combat Desertification (UNCCD), the four-day workshop (April 24-27, 2018) trained the participants in the use of an innovative land degradation monitoring tool by Conservation International, for the reporting process of UNCCD. 

The participants were trained in the use of the state-of-the-art tool called “Trends.Earth” developed by Conservation International.

Conservation International (CI) is an American non-profit environmental organization headquartered in Arlington, Virginia. Its goal is to protect nature as a source of food, fresh water, livelihoods and a stable climate.

CI’s work focuses on science, policy, and partnership with businesses and communities. The organization employs more than 1,000 people and works with more than 2,000 partners in 30 countries. CI has helped support 1,200 protected areas and interventions across 77 countries, safeguarding more than 601 million hectares of land, marine and coastal areas.

Hence, statement 1 is incorrect and statement 2 is correct.

Source:

https://economictimes.indiatimes.com/news/environment/pollution/desertification-land-degradation-drought-cost-india-2-54-of-its-gdp-study/articleshow/63944875.cms

https://www.conservation.org/Pages/default.aspx


  1. Which of the following diseases are under the list of Blueprint Priority Diseases of World Health Organization?
    1. Ebola
    2. Middle East respiratory syndrome (MERS)
    3. Zika
    4. Disease X
    5. Japanese Encephalitis

Select the correct answer using the code below:

a) 1, 2 and 3 only

b) 2 and 3 only

c) 1, 2, 3 and 4 only

d) 1, 2, 3, 4 and 5

Solution: c

Answer Justification:

List of Blueprint priority diseases

2018 annual review of the Blueprint list of priority diseases:

For the purposes of the R&D Blueprint, WHO has developed a special tool for determining the diseases and pathogens to prioritize for research and development in public health emergency contexts. This tool seeks to identify those diseases that pose a public health risk because of their epidemic potential and for which there are no, or insufficient, countermeasures. The diseases identified through this process are the focus of the work of R& D Blueprint. This is not an exhaustive list, nor does it indicate the most likely causes of the next epidemic.

The first list of prioritized diseases was released in December 2015.

Using a published prioritization methodology, the list was first reviewed in January 2017.

February 2018 – Second annual review:

The second annual review occurred 6-7 February, 2018. Experts consider that given their potential to cause a public health emergency and the absence of efficacious drugs and/or vaccines, there is an urgent need for accelerated research and development for*:

  • Crimean-Congo haemorrhagic fever (CCHF)
  • Ebola virus disease and Marburg virus disease
  • Lassa fever
  • Middle East respiratory syndrome coronavirus (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS)
  • Nipah and henipaviral diseases
  • Rift Valley fever (RVF)
  • Zika
  • Disease X

Disease X represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease, and so the R&D Blueprint explicitly seeks to enable cross-cutting R&D preparedness that is also relevant for an unknown “Disease X” as far as possible.

Hence, option (c) is correct.

 

Source: http://www.who.int/blueprint/priority-diseases/en/


  1. Which of the following statements are correct with respect to national parks and sanctuaries?
    1. No grazing of any shall be permitted in a National Park.
    2. No livestock shall be allowed to enter except where such livestock is used as a vehicle by a person authorised to enter such National Park.
    3. No grazing shall be permitted in a sanctuary.

Select the correct answer using the code below:

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: a

Justification:

National Park:

No grazing of any livestock shall be permitted in a National Park and no livestock shall be allowed to enter except where such livestock is used as a vehicle by a person authorised to enter such National Park.

Hence, statements 1 and 2 are correct.

Sanctuary:

The Chief Wildlife Warden may regulate, control or prohibit, in keeping with the interests of wildlife, the grazing or movement of livestock.

Hence, statement 3 is incorrect.

Source: http://envfor.nic.in/legis/wildlife/wildlife1c4.html


  1. Mangroves, saltwater crocodile, Indian python, wild pigs and rhesus monkeys are found in which of the following national park?

a) Bhitarkanika National Park

b) Sundarbans National Park

c) Nagarhole National Park

d) Periyar National Park

Solution: a

Justification:

Flora and Fauna of Bhitarkanika National Park

Flora: Mangrove species, casuarinas, and grasses like the indigo bush.

Fauna: The Park is home to the saltwater crocodile, Indian python, black ibis, wild boar, rhesus monkey, chital, darter, cobra, monitor lizard. Olive ridley turtles nest on Gahirmatha and other nearby beaches. Bhitarkanika has one of the largest populations of endangered saltwater crocodile in India and is globally unique in that, 10% of the adults exceed 6 m length. Nearly 1671 saltwater crocodiles inhabit the rivers and creeks. Around 3,000 saltwater crocodiles were born during 2014 annual breeding and nesting season.

Hence, option (a) is correct.

Source: https://en.wikipedia.org/wiki/Bhitarkanika_National_Park


  1. Which of the following statements is/are correct with respect to Agenda 21?
    1. It is a comprehensive plan of action to be taken globally, nationally and locally.
    2. It is a non-binding action plan.

Select the correct answer using the codes given below:

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

Solution: c

Explanation:

Agenda 21 is a comprehensive plan of action to be taken globally, nationally and locally by organizations of the United Nations System, Governments, and Major Groups in every area in which human impacts on the environment. 

Hence, statement 1 is correct.

Agenda 21 is a non-binding action plan of the United Nations with regard to sustainable development. It is a product of the Earth Summit (UN Conference on Environment and Development) held in Rio de Janeiro, Brazil, in 1992.

Hence, statement 2 is correct.

Source: https://sustainabledevelopment.un.org/outcomedocuments/agenda21


  1. Polybrominated diphenyl ethers (PBDEs) are found in which of the following substances?
    1. Plastics
    2. Furniture
    3. Electrical equipment
    4. Electronic devices
    5. Textiles

Select the correct answer using the code below:

a) 1, 2 and 3 only

b) 2 and 3 only

c) 1, 2, 3 and 4 only

d) 1, 2, 3, 4 and 5

Solution: d

Answer Justification:

What are PBDEs?

PBDEs are brominated hydrocarbons in which 2-10 bromine atoms are attached to the molecular structure.

PBDEs are used as flame retardants in a wide variety of products, including plastics, furniture, upholstery, electrical equipment, electronic devices, textiles and other household products.

At high temperatures, PBDEs release bromine radicals that reduce both the rate of combustion and dispersion of fire.

PBDEs exist as mixtures of distinct chemicals called congeners with unique molecular structures.

There are three types of commercial PBDE mixtures, including pentabromodiphenyl ether (pentaBDE), octabromodiphenyl ether (octaBDE) and decabromodiphenyl ether (decaBDE). DecaBDE is the most widely used PBDE globally.

Hence, option (d) is correct.

Source:  https://www.epa.gov/sites/production/files/2014-03/documents/ffrrofactsheet_contaminant_perchlorate_january2014_final_0.pdf


  1. Which of the following statements is/are correct with respect to shale gas?
    1. Fracking is the technique used to extract the gas.
    2. Sand and ceramic are used in its extraction.
    3. Shale rocks where gas is trapped usually have very low permeability compared to sandstone rocks.

Select the correct answer using the codes below:

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: d

Justification:

Throughout the world, different types of sedimentary rocks contain natural gas deposits, for example sandstones, limestones and shales. Sandstone rocks often have high permeability, which means that the tiny pores within the rock are well connected and gas can flow easily through the rock. In contrast, shale rocks where gas is trapped as a continuous accumulation throughout a large area usually have very low permeability, making gas production more complex and costly.

Hence, statement 3 is correct.

 The shale gas boom in recent years has been due to modern advancement in technology in hydraulic fracturing (fracking) to create extensive artificial fractures around well bores. Shale exists in sedimentary basins and typically forms about 80% of what a well will drill through. As a result, the main organic rich shales have already been identified in most regions of the world.

Hence, statement 1 is correct.

The biggest apprehension in exploitation of shale gas is the hydraulic fracturing job wherein large amount of water mixed with fracturing fluids is injected at high pressure into the reservoirs. The horizontal drilling within the shale gas bearing zones has to be enabled to receive gas trapped in the horizontal shales. The use of sand/ ceramic with high pressure water helps to fracture the shales and the resultant deposits of sand in the fractures, keeps the pores open for the gas to leak into the horizontal wells.

Hence, statement 2 is correct.

Source: http://indiaenergy.gov.in/wp-content/uploads/2017/09/Shale-gas-in-India-Prospects-and-Challenges-1.pdf


  1. Which of the following statements is/are correct with respect to Nuclear Reactions?
    1. The conditions needed for nuclear fusion are enormously high temperature and high pressure.
    2. The hydrogen bomb is based on thermonuclear fusion reaction.
    3. A nuclear bomb based on the fission of uranium or plutonium is placed at the core of the hydrogen bomb.

Select the correct answer using the codes given below:

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: d

Justification:

Nuclear fusion:

Currently all commercial nuclear reactors are based on nuclear fission. But there is another possibility of nuclear energy generation by a safer process called nuclear fusion. Fusion means joining lighter nuclei to make a heavier nucleus, most commonly hydrogen or hydrogen isotopes to create helium, such as 2H + 2H → 3He (+ n) It releases a tremendous amount of energy, according to the Einstein equation, as the mass of the product is little less than the sum of the masses of the original individual nuclei. Such nuclear fusion reactions are the source of energy in the Sun and other stars. It takes considerable energy to force the nuclei to fuse. The conditions needed for this process are extreme – millions of degrees of temperature and millions of pascals of pressure.

Hence, statement 1 is correct.

The hydrogen bomb is based on thermonuclear fusion reaction. A nuclear bomb based on the fission of uranium or plutonium is placed at the core of the hydrogen bomb. This nuclear bomb is embedded in a substance which contains deuterium and lithium. When the nuclear bomb (based on fission) is detonated, the temperature of this substance is raised to 107 K in a few microseconds. The high temperature generates sufficient energy for the light nuclei to fuse and a devastating amount of energy is released.

Hence, statements 2 and 3 are correct.

Source: NCERT Class X Chapter 14


  1. Which of the following statements is/are correct with respect to Chandrayaan-2?
    1. It is a totally indigenous mission.
    2. PSLV will be used as launch vehicle in this mission.
    3. It is comprised of an Orbiter, Lander and Rover.

Select the correct answer using the codes given below:

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: c

Justification:

Chandrayaan-2, India’s second mission to the Moon is a totally indigenous mission comprising of an Orbiter, Lander and Rover. After reaching the 100 km lunar orbit, the Lander housing the Rover will separate from the Orbiter. After a controlled descent, the Lander will soft land on the lunar surface at a specified site and deploy a Rover.

Hence, statement 1 and 3 are correct.

The mission will carry a six-wheeled Rover which will move around the landing site in semi-autonomous mode as decided by the ground commands. The instruments on the rover will observe the lunar surface and send back data, which will be useful for analysis of the lunar soil.

The Chandrayaan-2 weighing around 3290 kg and would orbit around the moon and perform the objectives of remote sensing the moon. The payloads will collect scientific information on lunar topography, mineralogy, elemental abundance, lunar exosphere and signatures of hydroxyl and water-ice.

GSLV-F10/Chandrayaan-2 Mission is planned during second half of 2018.

Hence, statement 2 is incorrect.

Source: https://www.isro.gov.in/gslv-f10-chandrayaan-2-mission


  1. Which of the following statements is/are correct with respect to Biofuels Policy – 2018?
    1. It allows use of surplus food grains for production of ethanol for blending with petrol.
    2. It allows damaged food grains like wheat, broken rice, Rotten Potatoes, unfit for human consumption for ethanol production.

Select the correct answer using the codes given below:

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

Solution: c

Explanation:

The Union Cabinet has approved National Policy on Biofuels – 2018.

Salient Features:

The Policy categorises biofuels as “Basic Biofuels” viz. First Generation (1G) bioethanol & biodiesel and “Advanced Biofuels” – Second Generation (2G) ethanol, Municipal Solid Waste (MSW) to drop-in fuels, Third Generation (3G) biofuels, bio-CNG etc. to enable extension of appropriate financial and fiscal incentives under each category.

The Policy expands the scope of raw material for ethanol production by allowing use of Sugarcane Juice, Sugar containing materials like Sugar Beet, Sweet Sorghum, Starch containing materials like Corn, Cassava, Damaged food grains like wheat, broken rice, Rotten Potatoes, unfit for human consumption for ethanol production.

Hence, statement 2 is correct.

Farmers are at a risk of not getting appropriate price for their produce during the surplus production phase. Taking this into account, the Policy allows use of surplus food grains for production of ethanol for blending with petrol with the approval of National Biofuel Coordination Committee.

Hence, statement 1 is correct.

With a thrust on Advanced Biofuels, the Policy indicates a viability gap funding scheme for 2G ethanol Bio refineries of Rs.5000 crore in 6 years in addition to additional tax incentives, higher purchase price as compared to 1G biofuels.

The Policy encourages setting up of supply chain mechanisms for biodiesel production from non-edible oilseeds, Used Cooking Oil, short gestation crops.

Roles and responsibilities of all the concerned Ministries/Departments with respect to biofuels has been captured in the Policy document to synergise efforts.

Source: http://pib.nic.in/newsite/PrintRelease.aspx?relid=179313


  1. Which of the following statements are correct with respect to viruses?
    1. Viruses have cells, which undergo rapid cell division.
    2. Viruses contain genes.

Select the correct answer using the codes given below:

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

Solution: b

Explanation:

A virus is a biological agent that reproduces inside the cells of living hosts. When infected by a virus, a host cell is forced to produce thousands of identical copies of the original virus at an extraordinary rate. Unlike most living things, viruses do not have cells that divide; new viruses are assembled in the infected host cell.

Hence, statement 1 is incorrect.

But unlike still simpler infectious agents, viruses contain genes, which gives them the ability to mutate and evolve. Over 5,000 species of viruses have been discovered.

Hence, statement 2 is correct.

Source: https://en.wikipedia.org/wiki/Introduction_to_viruses#Effects_on_the_host_cell


  1. As per the guideline to create Eco Sensitive Zones (ESZs), which of the following statements are correct?
    1. It prohibits tourism activities like flying over protected areas.
    2. Commercial use of natural water resources, including groundwater harvesting is permitted in the protected areas.

Select the correct answer using the codes given below:

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

Solution: a

Explanation:

It prohibits tourism activities like flying over protected areas in an aircraft or hot air balloon, and discharge of effluents and solid waste in natural water bodies or terrestrial areas.

Hence, statement 1 is correct.

Felling of trees, drastic change in agriculture systems and commercial use of natural water resources, including groundwater harvesting and setting up of hotels and resorts, are the activities regulated in the areas.

Hence, statement 2 is incorrect.

Activities permitted in the areas include ongoing agriculture and horticulture practices by local communities, rainwater harvesting and organic farming, adoption of green technology and use of renewable energy sources.

Source: http://www.moef.gov.in/sites/default/files/1%20Guidelines%20for%20Eco-Sensitive%20Zones%20around%20Protected%20Areas.pdf


  1. Which of the following statements is/are correct with respect to rainbow?
    1. The pattern of it always appear as VIBGYOR from top to bottom.
    2. A rainbow is a demonstration of the dispersion, refraction and total internal reflection of light.
    3. Bright sunlight, suspended droplets of water and the proper angle of sighting are the three necessary components for viewing.

Select the correct answer using the codes below:

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: b

Justification:

A rainbow is a meteorological phenomenon that is caused by total internal reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multi-coloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.

Hence, statement 2 is correct.

The net effect of the vast array of droplets is that a circular arc of ROYGBIV from top to bottom is seen across the sky.

Hence, statement 1 is incorrect.

Rainbows are not limited to the dispersion of light by raindrops. The splashing of water at the base of a waterfall caused a mist of water in the air that often results in the formation of rainbows. A backyard water sprinkler is another common source of a rainbow. Bright sunlight, suspended droplets of water and the proper angle of sighting are the three necessary components for viewing one of nature’s most splendid masterpieces.

Hence, statement 3 is correct.

Source: https://www.google.co.in/search?q=formation+of+rainbow&oq=formation+of+rainbow&aqs=chrome..69i57j0l5.9938j0j7&sourceid=chrome&ie=UTF-8


  1. Recently, NASA launched InSight spacecraft to study which of the following celestial bodies?

a) Moon

b) Mars

c) Sun

d) Saturn

Solution: b

Justification:

NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) launched on a United Launch Alliance (ULA) Atlas V 401 rocket on May 5, 2018 from Space Launch Complex-3 at Vandenberg Air Force Base in California.

InSight is the first interplanetary mission to launch from the West Coast, and will be the first mission to look deep beneath the Martian surface. It will study the planet’s interior by measuring its heat output and listening for mars quakes. InSight will use the seismic waves generated by mars quakes to develop a map of the planet’s deep interior. The resulting insight into Mars’ formation will provide a better understanding of how other rocky planets, including Earth were created.

Hence, option (b) is correct.

Source:

https://blogs.nasa.gov/insight/2018/05/05/nasas-insight-spacecraft-now-on-its-way-to-mars/


  1. Birds Following Army Ants is an example for which of the following types of symbiotic relationship between organisms?

a) Mutualism

b) Parasitism

c) Commensalism

d) Competition

Solution: c

Justification:

Commensalism is a type of symbiotic relationship between organisms in which one organism benefits without harming the other in any way.

Other types of symbiotic relationships include mutualism, in which both the organisms involved benefit from each other, and parasitism, where one of the organisms is benefited, while the other is harmed.

Many birds form a commensal relationship with some species of ants like the army ants. A great number of army ants trail on the forest floor, and while moving, stir up many insects lying in their path. The birds follow these army ants and eat up the insects that try to escape from them. The birds benefit by catching their prey easily, while the army ants are totally unaffected.

Hence, option (c) is correct.

Source: https://sciencestruck.com/examples-of-commensalism

 


  1. What is ‘GREENE’?

a) An E-Waste awareness initiative.

b) A green energy initiative.

c) An initiative to impart environmental education.

d) An initiative for paperless transactions through e-commerce.

Solution: a

Justification:

GREENE, An E-Waste awareness initiative supported by Ministry of Electronics and Information Technology (MeitY), Government of India.

The Ministry of Electronics and Information Technology (MeitY) has initiated the project “Awareness Programme on Environmental Hazards of Electronic waste” on March 31, 2015. This project is under the ‘Digital India’ initiative of the Government of India. The project is expected to have far reaching and significant impact on the growth of the country as it focuses on reuse and recycling of e-waste, which has the potential to conserve natural resources. The project has three components viz., Content Development, Inventory Assessment and Awareness Generation amongst different stakeholders. The project will help in effective implementation of E-waste Management Rules, 2016.

Hence, option (a) is correct.

Source: http://greene.gov.in/


  1. Which of the following statements is/are correct with respect to methane emissions?
    1. Methane’s lifetime in the atmosphere is much longer than carbon dioxide.
    2. Natural processes in soil and chemical reactions in the atmosphere help remove methane from the atmosphere.
    3. Methane is more efficient at trapping radiation than Carbon Dioxide.

Select the correct answer using the codes below:

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: b

Justification:

Human activities emitting methane include leaks from natural gas systems and the raising of livestock. Methane is also emitted by natural sources such as natural wetlands. In addition, natural processes in soil and chemical reactions in the atmosphere help remove CH4 from the atmosphere.

Hence, statement 2 is correct.

Methane’s lifetime in the atmosphere is much shorter than carbon dioxide (CO2), but CH4 is more efficient at trapping radiation than CO2. Pound for pound, the comparative impact of CH4 is more than 25 times greater than CO2 over a 100-year period.

Hence, statement 1 is incorrect and statement 3 is correct.

Source: https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane


  1. Which of the following statements is/are correct with respect to Genome Project-Write?
    1. It includes development of technologies for synthesis and testing of many genomes of microbes, plants and animals.
    2. Human Genome Project (HGP) – Write is a sub project of it to build an artificial human genome.

Select the correct answer using the codes given below:

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

Solution: c

Explanation:

The Genome Project – Write (also known as GP-Write) includes sub-projects like Human Genome Project-Write (HGP-Write), formally announced on 2 Jun 2016 is an extension of Genome Projects (aimed at reading genomes since 1984), now to include development of technologies for synthesis and testing of many genomes of microbes, plants and animals. This leverages two decades of work on Synthetic Biology and Artificial gene synthesis.

The newly created GP-Write project will be managed by the Center of Excellence for Engineering Biology, a new non-profit organization. The researchers expect that the ability to synthesize large portions of many genomes would result in many scientific and medical advances.

Human Genome Project–write (HGP-write), now underway to synthesise a human genome from scratch. The original HGP was a “read” in that it used chemicals and instruments to decipher the genome for the first time. The new project, its proponents say, is to write or build an artificial human genome with sophisticated bioengineering tools.

Hence, both the statements are correct.

Source:

http://www.thehindu.com/opinion/op-ed/Human-Genome-Project-The-%E2%80%98Write%E2%80%99-track/article14401695.ece

https://en.wikipedia.org/wiki/Genome_Project-Write


  1. Which of the following statements is/are correct with respect to MUNTRA tank?
    1. It is an unmanned tank.
    2. It can be deployed for surveillance and mine clearing.
    3. It can’t be deployed in areas where nuclear radiation risk is high.

Select the correct answer using the codes below:

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: a

Justification:

Muntra is India’s first unmanned tank developed by the Defence Research and Development Organisation (DRDO).

Muntra has three variants:

  • Muntra-S has been developed for unmanned surveillance missions.
  • Muntra-M is built for detecting mines.
  • Muntra-N, will be deployed in areas where nuclear radiation or bio weapon risk is high.

Hence, statements 1 and 2 are correct and statement 3 is incorrect.

Source: https://en.wikipedia.org/wiki/Muntra

 


  1. Which of the following chemicals are used for cloud seeding?
    1. Calcium carbide
    2. Sodium Chloride
    3. Dry ice
    4. Liquid propane

Select the correct answer using the codes given below:

a) 4 only

b) 3 and 4 only

c) 1 and 4 only

d) 1, 2, 3 and 4

Solution: d

Justification:

Carbon dioxide in the form of dry ice is also important in the making of artificial rain. This chemical is a colorless gas with chemical compound CO2. While carbon monoxide is carbon atom that bonds only with one oxygen atom, carbon dioxide bonds with two atoms and is not as dangerous as monoxide one. When it is in the form of ice, carbon dioxide will help to weigh down the clouds and press the trapped water to fall down to surface of the earth. Dry ice is not similar to ordinary ice so it functions purely as additional weight to the cloud and does not contain water.

Propane is an alkane compound with three carbon atoms. It has the chemical formula of C3H8. Propane is a common substance used as fuel is a natural gas that often is colorless but under certain circumstance can turn into liquid form. Propane gas as cloud seeding material acts as a pusher to encourage the clouds to precipitate. The liquid form of it will also trigger the clouds to release a liquid form of itself, further cause rain. Propane needs other chemical to be able to properly run its function in cloud seeding. Regardless, propane is important in the process of artificial rain. 

During agitation state calcium carbide is used in the making of artificial rain. Calcium carbide along with calcium oxide acts as absorbers of water vapour. It consists of salt and urea or ammonium nitrate. This chemical is a calcium compound with formula CAC2. It is usually colorless but can also appear whitish. To produce calcium carbide, lime and coke mixture in an electric arc furnace reaction will result in calcium carbide. Furthermore, the role in artificial rain is to trigger precipitation in the sky clouds.

Alternative chemical beside silver iodide to create artificial rain is sodium chloride. Sodium chloride is a chemical compound with formula NaCl. The formation of sodium chloride is one portion of sodium and one portion of chloride. Commonly known as salt, it is an ionic compound that can also acts as denser in artificial rain making. The chemical will make the cloud dense with big beads of water, further pushing them to create precipitation and drop rain onto the earth’s surface. The use of it is considered to be more expensive compared to silver iodide and is only used occasionally during extreme dry season. 

Hence, option (d) is correct.

Source: https://azchemistry.com/chemicals-used-in-artificial-rain