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SOLUTIONS – INSIGHTS REVISION TEST for Preliminary Exam 2018: Test – 47(Environment and General Science)


SOLUTIONS 

INSIGHTS REVISION TEST for Preliminary Exam 2018: Test – 47(Environment and General Science)


 

1.Which of the following statements is/are correct about Nuclear Reactors in India?

  1. Breeder reactors produce equal amount of fuel that they consume.
  2. In the thorium fuel cycle, thorium 232 is transmuted into the fissile isotope uranium 233.

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

Justification:

Fast Breeder Reactors

For the second stage of the Nuclear Power Generation Programme, the Indira Gandhi Centre for Atomic Research (IGCAR) is pursuing development of sodium cooled fast breeder reactors and associated fuel cycle technologies. Breeder reactors produce more fuel than they consume. Hence, statement 1 is incorrect.

Thorium Based Reactors

Nuclear power employing closed fuel cycle is the only sustainable option for meeting a major part of the world energy demand. World resources of thorium are larger than those of uranium. Thorium, therefore is, widely viewed as the ‘fuel of the future’. The Indian Nuclear Power Programme Stage-3 aims at using thorium as fuel for power generation on a commercial scale. In the thorium fuel cycle, thorium 232 is transmuted into the fissile isotope uranium 233 which is a nuclear fuel. As a part of this programme, BARC has been developing a 300 MWe Advanced Heavy Water Reactor (AHWR). Fuelled by thorium and using light water as coolant and heavy water as moderator, this reactor will have several advanced passive safety features.

Hence, statement 2 is correct.


  1. Which of the following statements is/are correct about Ramjet Engines?
    1. Ramjet Engines carry oxidiser along with the fuel for combustion to produce thrust.
    2. Scramjet engine is an improvement over the ramjet engine as it efficiently operates at supersonic speeds.

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: d

Justification:

A ramjet is a form of air-breathing jet engine that uses the vehicle’s forward motion to compress incoming air for combustion without a rotating compressor. Fuel is injected in the combustion chamber where it mixes with the hot compressed air and ignites. A ramjet-powered vehicle requires an assisted take-off like a rocket assist to accelerate it to a speed where it begins to produce thrust.

Hence, statement 1 is incorrect.

Ramjets work most efficiently at supersonic speeds around Mach 3 (three times the speed of sound) and can operate up to speeds of Mach 6. However, the ramjet efficiency starts to drop when the vehicle reaches hypersonic speeds.

A scramjet engine is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and allows supersonic combustion. Thus it is known as Supersonic Combustion Ramjet, or Scramjet. 

Hence, statement 2 is incorrect.

Source: https://www.isro.gov.in/launchers/isro%E2%80%99s-scramjet-engine-technology-demonstrator-successfully-flight-tested


  1. Which of the following statements is/are correct about Traditional Knowledge Digital Library (TKDL)?
    1. It is an initiative of India to prevent misappropriation of country’s traditional medicinal knowledge at International Patent Offices.
    2. Council of Scientific and Industrial Research (CSIR) has created it.
    3. Council of Scientific and Industrial Research (CSIR) is the custodian of it.

Select the correct answer using the codes below.

a) 1 only

b) 1 and 2 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: d

Justification:

CSIR has created and is the custodian of Traditional Knowledge Digital Library (TKDL).

Henc statement 2 and 3 are correct.

TKDL is a pioneer initiative of India to prevent misappropriation of country’s traditional medicinal knowledge at International Patent Offices (hence statement 3 is correct) on which healthcare needs of more than 70% population and livelihood of millions of people in India is dependent. Its genesis dates back to the Indian effort on revocation of patent on wound healing properties of turmeric at the USPTO. Besides, in 2005, the TKDL expert group estimated that about 2000 wrong patents concerning Indian systems of medicine were being granted every year at international level, mainly due to the fact that India’s traditional medicinal knowledge which exists in local languages such as Sanskrit, Hindi, Arabic, Urdu, Tamil etc. is neither accessible nor comprehensible for patent examiners at the international patent offices.

Source:

http://www.tkdl.res.in/tkdl/LangFrench/common/Abouttkdl.asp?GL=Eng

India Year Book 2018


 

  1. A high altitude research station called HIMANSH is situated in:

a) Sea ice Arctic region

b) Sea ice of Antarctic region

c) Himalayas

d) Ice sheets of Greenland

Solution: c

Justification:

As part of the Indian government’s initiatives to better study and quantify the Himalayan glacier responses towards the climate change, National Centre for Antarctic and Ocean Research (NCAOR), Goa, under the Ministry of Earth Sciences has established a high altitude research station in Himalaya called HIMANSH (literally meaning, a slice of ice), situated above 13,500 ft (> 4000 m) at a remote region in Spiti, Himachal Pradesh.

Source: http://pib.nic.in/newsite/PrintRelease.aspx?relid=151572


  1. Which of the following statements is/are correct about Spot Picker Robot?
    1. It is an indigenous robot.
    2. It is used in the field of proteomics.

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: c

Justification:

Spot Picker Robot is a state-of-the-art technology for precise protein spot excision. It is indigenously developed by Bhabha Atomic Research Centre.

Hence statement 1 is correct.

It’s a three axes robotic system with image processing algorithms designed for precisely locates and identifies the protein spots from 2D electrophoresis gel. It picks and transfers the protein for further analysis, thus enhancing the data quality and reliability in the field of proteomics. This system has of immense use in proteomics workflow required for identification of new proteins to develop biomarkers and new drug targets in many diseases.

Hence statement 2 is correct.

Source: http://www.barc.gov.in/publications/nl/2013/2013010205.pdf


  1. Which of the following pairs of DRDO systems and their details is/are correctly matched?
DRDO SystemsDetails
1. SANGRAHAA compact communication electronic warfare suit.
2. SAMYUKTAAn indigenous EW programme for Navy
3. SUJAVA software and integration intensive and meant for indigenous development of an integrated EW system.

 

Select the correct answer using the codes below.

a) 1 only

b) 2 only

c) 3 only

d) None of the above

Solution: d

Justification:

SANGRAHA EW SYSTEM

Development of all five types of electronic warfare (EW) systems have been completed under the project SANGRAHA, (an indigenous EW programme for Navy) and demonstrated to the users. Field evaluation of the systems for airborne platforms are in various stages of evaluation and that for the submarine platform, has been completed successfully. Navy required two systems for their submarines-one has been delivered and second is nearing completion.

SAMYUKTA EW SYSTEM

SAMYUKTA is a joint programme of DRDO and Indian Army. This programme is software and integration intensive and meant for indigenous development of an integrated EW system. A stand-alone jammer (SAJ) after completing evaluation in the factory, has been evaluated in the field by users and inputs from this evaluation are being incorporated in electronic counter measure (ECM) for non-com segment, in all three frequency bands namely low, mid and high bands. With this development, ECM for non-com segment, has been completed and entities are under evaluation. The system comprises vehicles having the capabilities for surveillance, interception, monitoring, analysis and jamming of all communication and radar signals.

SUJAV Clusters System

It is a compact communication electronic warfare suit. The system has got direction finding, search and monitoring capabilities covering 30-1000 MHz and jamming in 30-500 MHz frequency range. The system was deployed in J&K by Army and Rajasthan sectors achieving satisfactory performance. Indian Navy has also placed order for the production of 8 such system (called Drishti) for off shore and on shore applications. Indian Army has placed order for 7 Sujav clusters consisting of three Electronic Support Measure (ESM) and one Electronic Counter Measure (ECM) station. One Sujav clusters system has been successfully evaluated in North East and Jammu region.

None of the pairs are correctly matched.

Source: http://www.drdo.gov.in/drdo/English/index.jsp?pg=tech_electronics.jsp


  1. Muon and tau are associated which of the following particles?
    1. Neutrinos
    2. Boson or God Particles

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: a

Justification:

Neutrinos are fundamental particles belonging to the lepton family. They come in three flavours, one associated with electrons and the others with their heavier cousins the muon and the Tau. According to standard model of particle physics, they are mass less. However recent experiments indicate that these charge-neutral fundamental particles, have finite but small mass which is unknown. They oscillate between flavours as they propagate. Determination of neutrino masses and mixing parameters is one of the most important open problems in physics today. The Iron Calorimeter (ICAL) detector is designed to address some of these key open problems in a unique way. Over the years this underground facility is expected to develop into a full-fledged underground science laboratory for other studies in physics, biology, geology, hydrology etc.

 

Source: http://www.ino.tifr.res.in/ino/index.php


  1. Which of the following statements is/are correct about stem cells?
    1. Stem cells are undifferentiated cells.
    2. Specialized cells are the differentiated cells.
    3. Induced pluripotent cells (iPSCs) are derived from adult somatic cells.

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:

Stem cell, an undifferentiated cell that can divide to produce some offspring cells that continue as stem cells and some cells that are destined to differentiate (become specialized). Stem cells are an ongoing source of the differentiated cells that make up the tissues and organs of animals and plants. There is great interest in stem cells because they have potential in the development of therapies for replacing defective or damaged cells resulting from a variety of disorders and injuries, such as Parkinson disease, heart disease, and diabetes. There are two major types of stem cells: embryonic stem cells and adult stem cells, which are also called tissue stem cells.

Hence, statements 1 and 2 are correct.

Adult cells that become reprogrammed in this way are known as induced pluripotent stem cells (iPS).

Hence, statement 3 is correct.

Source: https://www.britannica.com/science/stem-cell#ref272801


 

  1. Consider the following statements.
    1. Bioleaching is used essentially for the recovery of copper, uranium and gold.
    2. Biosparging can be used to reduce concentrations of petroleum constituents that are dissolved in groundwater.
    3. Bioaugmentation can be involved in bioremediation.

Which of the above statements is/are correct?

a) 1 and 2 only

b) 2 and 3 only

c) 1 and 3 only

d) 1, 2 and 3

Solution: d

Justification:

Bioleaching is a simple and effective technology for metal extraction from low-grade ores and mineral concentrates. Metal recovery from sulfide minerals is based on the activity of chemolithotrophic bacteria, mainly Thiobacillus ferrooxidans and T. thiooxidans, which convert insoluble metal sulfides into soluble metal sulfates. Non-sulfide ores and minerals can be treated by heterotrophic bacteria and by fungi. In these cases metal extraction is due to the production of organic acids and chelating and complexing compounds excreted into the environment. At present bioleaching is used essentially for the recovery of copper, uranium and gold, and the main techniques employed are heap, dump and in situ leaching. Tank leaching is practised for the treatment of refractory gold ores. Bioleaching has also some potential for metal recovery and detoxification of industrial waste products, sewage sludge and soil contaminated with heavy metals.

Hence, statement 1 is correct.

Biosparging is an in-situ remediation technology that uses indigenous microorganisms to bio-degrade organic constituents in the saturated zone. In biosparging, air (or oxygen) and nutrients (if needed) are injected into the saturated zone to increase the biological activity of the indigenous microorganisms. Biosparging can be used to reduce concentrations of petroleum constituents that are dissolved in groundwater, adsorbed to soil below the water table, and within the capillary fringe. Although constituents adsorbed to soils in the unsaturated zone can also be treated by biosparging, bioventing is typically more effective for this situation.

Hence, statement 2 is correct.

Bioremediation strategies can involve natural attenuation, bioaugmentation, or biostimulation and can take place in situ or ex situ.

Hence, statement 3 is correct.

Source: https://www.epa.gov/sites/production/files/2014-03/documents/tum_ch8.pdf

https://www.sciencedirect.com/science/article/pii/S0168644597000363

https://www.sciencedirect.com/topics/immunology-and-microbiology/bioaugmentation


 

  1. Which of the following statements is/are correct about Mission Indradhanush?
    1. It ensures full immunization with all available vaccines for children up to two years and pregnant women.
    2. Under Mission Indradhanush, all the vaccines provided under Universal Immunization Program are not administered.
    3. Intensified Mission Indradhanush (IMI) programme aims to reach who have been left uncovered under the routine immunisation programme.

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: c

Justification:

The ultimate goal of Mission Indradhanush is to ensure full immunization with all available vaccines for children up to two years and pregnant women.

Hence, statement 1 is correct.

Keeping up with its commitment to improve immunization coverage and addressing equity, MoHFW, GoI has implemented various intensification strategies including its flagship program, “Mission Indradhanush” launched in December 2014. Mission Indradhanush aimed to fully immunize more than 90% of new-borns by 2020 through innovative and planned approaches to reach all children. Under Mission Indradhanush, all the vaccines provided under Universal Immunization Program were administered to children and pregnant women. A total of 528 districts were covered during the various phases of Mission Indradhanush.             

Hence, statement 2 is correct.

Intensified Mission Indradhanush (IMI) programme, Government of India aims to reach each and every child under two years of age and all those pregnant women who have been left uncovered under the routine immunisation programme. The special drive will focus on improving immunization coverage in select districts and cities to ensure full immunization to more than 90% by December 2018. The achievement of full immunisation under Mission Indradhanush to at least 90% coverage was to be achieved by 2020 earlier. With the launch of IMI, achievement of the target has now been advanced. 

Hence, statement 3 is correct.

Source: http://www.missionindradhanush.in/


  1. Which of the following pairs of stains and the flu is/are correctly matched?
StrainsFlu
1. H1N1Swine Flu
2. H5N1Hong Kong Flu
3. H3N2Bird Flu

 

Select the correct answer using the codes below.

a) 1 only

b) 2 only

c) 1 and 3 only

d) None of these

Solution: a

Justification:

Wild aquatic birds are the natural hosts for a large variety of influenza A virus. Occasionally, viruses are transmitted to other species and may then cause devastating outbreaks in domestic poultry or give rise to human influenza pandemics. The type A viruses are the most virulent human pathogens among the three influenza types and cause the severest disease. The influenza A virus can be subdivided into different serotypes based on the antibody response to these viruses. The serotypes that have been confirmed in humans, ordered by the number of known human pandemic deaths, are:

H1N1, which caused Spanish Flu in 1918, and Swine Flu in 2009

H2N2, which caused Asian Flu in 1957

H3N2, which caused Hong Kong Flu in 1968

H5N1, which caused Bird Flu in 2004

H7N7, which has unusual zoonotic potential

H1N2, endemic in humans, pigs and birds etc.

Hence, only pair 1 is matched correctly.

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


 

  1. Which of the following statements is/are correct about Li-Fi (Light Fidelity)?
    1. It can transmit data only over visible light spectrum.
    2. It operates across lower bandwidth in comparison to Wi-Fi.

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: d

Justification:

Li-Fi (Light Fidelity) is a technology for wireless communication between devices using light to transmit data. In its present state only LED lamps can be used for the transmission of visible light. The term was first introduced by Harald Haas during a 2011 TED Global talk in Edinburgh.

In technical terms, Li-Fi is a visible light communications system that is capable of transmitting data at high speeds over the visible light spectrum, ultraviolet and infrared radiation.

In terms of its end use the technology is similar to Wi-Fi. The key technical difference is that Wi-Fi uses radio frequency to transmit data. Using light to transmit data allows Li-Fi to offer several advantages like working across higher bandwidth, working in areas susceptible to electromagnetic interference (e.g. aircraft cabins, hospitals) and offering higher transmission speeds. The technology is actively being developed by several organisations across the globe.

Hence, both the statements are incorrect.

Source: https://en.wikipedia.org/wiki/Li-Fi

 


  1. Which of the following statements is/are correct about GSLV Mk III?
    1. It is a three-stage heavy lift launch vehicle.
    2. It can carry payloads to both Geosynchronous Transfer Orbit (GTO) and Low Earth Orbit (LEO).

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: c

Justification:

GSLV Mk III is a three-stage heavy lift launch vehicle developed by ISRO. The vehicle has two solid strap-ons, a core liquid booster and a cryogenic upper stage.

GSLV Mk III is designed to carry 4 ton class of satellites into Geosynchronous Transfer Orbit (GTO) or about 10 tons to Low Earth Orbit (LEO), which is about twice the capability of GSLV Mk II.

The two strap-on motors of GSLV Mk III are located on either side of its core liquid booster. Designated as ‘S200’, each carries 205 tons of composite solid propellant and their ignition results in vehicle lift -off. S200s function for 140 seconds. During strap-ons functioning phase, the two clustered Vikas liquid Engines of L110 liquid core booster will ignite 114 sec after lift -off to further augment the thrust of the vehicle. These two engines continue to function after the separation of the strap-ons at about 140 seconds after lift -off.

The first experimental flight of LVM3, the LVM3-X/CARE mission lifted off from Sriharikota on December 18, 2014 and successfully tested the atmospheric phase of flight. Crew module Atmospheric Re-entry Experiment was also carried out in this flight. The module re-entered, deployed its parachutes as planned and splashed down in the Bay of Bengal.

The first developmental flight of GSLV Mk III, the GSLV-Mk III-D1 successfully placed GSAT-19 satellite to a Geosynchronous Transfer Orbit (GTO) on June 05, 2017 from SDSC SHAR, Sriharikota.

Hence, both the statements are correct.

Source: https://www.isro.gov.in/launchers/gslv-mk-iii

 


  1. Which of the following statements is/are correct about Brown dwarfs?
    1. They are astronomical object that is intermediate between a planet and a star.
    2. They do not reach stable luminosities.
    3. They are brown in colour.

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:

Brown dwarf, astronomical object that is intermediate between a planet and a star. Brown dwarfs usually have a mass less than 0.075 that of the Sun, or roughly 75 times that of Jupiter. (This maximum mass is a little higher for objects with fewer heavy elements than the Sun.) Many astronomers draw the line between brown dwarfs and planets at the lower fusion boundary of about 13 Jupiter masses. The difference between brown dwarfs and stars is that, unlike stars, brown dwarfs do not reach stable luminosities by thermonuclear fusion of normal hydrogen.

Hence, statement 1 and 2 is correct.

Both stars and brown dwarfs produce energy by fusion of deuterium (a rare isotope of hydrogen) in their first few million years. The cores of stars then continue to contract and get hotter until they fuse hydrogen. However, brown dwarfs prevent further contraction because their cores are dense enough to hold themselves up with electron degeneracy pressure. (Those brown dwarfs above 60 Jupiter masses begin to fuse hydrogen, but they then stabilize, and the fusion stops.)

Brown dwarfs are not actually brown but appear from deep red to magenta depending on their temperature. Objects below about 2,200 K, however, do actually have mineral grains in their atmospheres. The surface temperatures of brown dwarfs depend on both their mass and their age. The most massive and youngest brown dwarfs have temperatures as high as 2,800 K, which overlaps with the temperatures of very low-mass stars, or red dwarfs. (By comparison, the Sun has a surface temperature of 5,800 K.) All brown dwarfs eventually cool below the minimum main-sequence stellar temperature of about 1,800 K. The oldest and smallest can be as cool as about 300 K.

Hence, statement 3 is incorrect.

Source: https://www.britannica.com/science/brown-dwarf

 


  1. Israel has launched Venus satellite. It is:

a) A satellite to study the atmosphere of Planet Venus.

b) An earth-observation micro-satellite.

c) A satellite to study the terrestrial planets.

d) A nano-satellite.

 

Solution: b

 

Justification:

Israel has launched the country’s first environmental research satellite in a joint venture between the Israel Space Agency (ISA) and its French counterpart CNES.

The Venus satellite (Vegetation and Environment Monitoring New Micro-Satellite) is an earth-observation micro-satellite.

The satellite’s goal is to obtain high-resolution photographs of specific sites to track environmental issues such as desertification, erosion, pollution, natural disasters, and other phenomena linked to climate change.

The satellite will be able to take repeated photos of the same spot in the same light conditions (accounting for the position of the sun), allowing for more accurate tracking of changing environmental issues.

Hence, option (b) is correct.

Source: https://venus.cnes.fr/en/VENUS/GP_satellite.htm

 


  1. GOLD and ICON are recently in news. Which of the statements is/are correct about them?
    1. They will team up to explore the stratosphere.
    2. They will measure how upper atmosphere changes in response to hurricanes and geomagnetic storms.
    3. They will find evidences for a theoretical model about El Nino’s repercussions.

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:

U.S. space agency National Aeronautics and Space Administration (NASA) – to explore a little-understood area 60 miles (96 KM) above Earth’s surface. The missions are named GOLD and ICON.

The Global-scale Observations of the Limb and Disk (GOLD) mission was launched recently, and the designed spacecraft Ionospheric Connection Explorer (ICON) will be launched later.

GOLD and ICON will team up to explore the ionosphere.

Hence, statement 1 is incorrect.

These layers of near-Earth space are increasingly becoming a part of human domain as it is home to radio signals used to guide airplanes, ships and Global Positioning System satellites.

The missions’ goals is to measure how upper atmosphere changes in response to hurricanes and geomagnetic storms.

Hence, statement 2 is correct.

GOLD will also explore how the upper atmosphere reacts to geomagnetic storms, which are temporary disturbances of Earth’s magnetic field set off by solar activity.

The agency is hoping to find evidences for a theoretical model about El Nino’s repercussions on the ionosphere.

Hence, statement 3 is correct.

Source: https://www.nasa.gov/feature/goddard/2018/two-heads-are-better-than-one-icon-gold-teaming-up-to-explore-earths-interface-to-space


  1. Which of the following statements is/are correct?
    1. Human ears can hear the sounds in the frequency range 20Hz – 20 kHz.
    2. Dogs can hear sounds of frequencies higher than 20 kHz.
    3. The ultrasound equipment work at frequencies lower than 20 kHz.

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:

Sounds of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear. Such sounds are called inaudible. On the higher side, sounds of frequencies higher than about 20,000 vibrations per second (20 kHz) are also not audible to the human ear. Thus, for human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz.

Hence, statement 1 is correct.

Some animals can hear sounds of frequencies higher than 20,000 Hz. Dogs have this ability. The police use high frequency whistles which dogs can hear but humans cannot.

Hence, statement 2 is correct.

The ultrasound equipment, familiar to us for investigating and tracking many medical problems, works at frequencies higher than 20,000 Hz.

Hence, statement 3 is incorrect.

Source: NCERT Class VIII Science, chapter 13


 

  1. Which of the following pairs of animals and their major excretory product is matched correctly?
AnimalsMajor excretory products
1. FishesUric acid
2. SnakesAmmonia
3. HumansUrea

 

Select the correct answer using the codes below.

a) 1 only

b) 2 only

c) 3 only

d) None of the above

 

Solution: c

 

Justification:

The way in which waste chemicals are removed from the body of the animal depends on the availability of water.

Aquatic animals like fishes, excrete cell waste as ammonia which directly dissolves in water.

Some land animals like birds, lizards, snakes excrete a semi-solid, white coloured compound (uric acid).

The major excretory product in humans is urea.

Hence, only pair 3 is correctly matched.

Source: NCERT Class VII, Chapter 11.


 

  1. Which of the following statements is/are correct about cell wall?
    1. Plants, fungi and bacteria have cell walls.
    2. Cell walls permit the cells to withstand very dilute external media without bursting.

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: c

Justification:

Plant cells, in addition to the plasma membrane, have another rigid outer covering called the cell wall. The cell wall lies outside the plasma membrane. The plant cell wall is mainly composed of cellulose. Cellulose is a complex substance and provides structural strength to plants. When a living plant cell loses water through osmosis there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.

Cell walls permit the cells of plants, fungi and bacteria to withstand very dilute (hypotonic) external media without bursting. In such media the cells tend to take up water by osmosis. The cell swells, building up pressure against the cell wall. The wall exerts an equal pressure against the swollen cell. Because of their walls, such cells can withstand much greater changes in the surrounding medium than animal cells.

Hence, both the statements are correct.

Source: NCERT Class IX, chapter 5


  1. Recently flammable ice was in news. It is:

a) A gas hydrate

b) A comet

c) An explosive

d) A pyroclastic substance

Solution: a

Justification:

Scientists have solved a molecular puzzle explaining the natural formation of gas hydrates, a type of flammable crystal also known as “the ice that burns.”

China has successfully produced natural gas from methane hydrate, also known as “flammable ice”, in South China Sea.

Hence, option (a) is correct.

Source: https://www.livescience.com/62276-gas-hydrates-flammable-ice.html