NCERT NEET Biology English Medium Part-1 | Chapter 27 : Microbes in human welfare

NCERT NEET Biology English Medium Part-1 | Chapter 27 : Microbes in Human Welfare

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Question 1. Which of the following microorganisms is primarily responsible for the coagulation and partial digestion of milk proteins during curd formation?

1. Saccharomyces cerevisiae.
2. Lactobacillus.
3. Aspergillus niger.
4. Acetobacter aceti.

Answer: b. Lactobacillus.

Question 2. What specific nutritional quality of milk is improved when it is converted into curd by Lactic Acid Bacteria (LAB)?

1. Vitamin A.
2. Vitamin C.
3. Vitamin B12.
4. Vitamin D.

Answer: c. Vitamin B12.

Question 3. In the human stomach, which of the following roles is predominantly played by Lactic Acid Bacteria?

1. Digestion of cellulose.
2. Checking disease-causing microbes.
3. Absorption of lipids.
4. Secretion of intrinsic factor.

Answer: b. Checking disease-causing microbes.

Question 4. The puffed-up appearance of dough used for making dosa and idli is due to the production of which gas?

1. Oxygen.
2. Nitrogen.
3. Carbon dioxide.
4. Methane.

Answer: c. Carbon dioxide.

Question 5. Which of the following microorganisms is commonly referred to as baker's yeast?

1. Saccharomyces cerevisiae.
2. Streptococcus pyogenes.
3. Propionibacterium sharmanii.
4. Penicillium notatum.

Answer: a. Saccharomyces cerevisiae.

Question 6. 'Toddy', a traditional drink in some parts of southern India, is made by fermenting sap from which plant?

1. Bamboo.
2. Soybean.
3. Palm.
4. Sugarcane.

Answer: c. Palm.

Question 7. The large holes found in 'Swiss cheese' are a result of the production of large amounts of carbon dioxide by which bacterium?

1. Propionibacterium sharmanii.
2. Lactobacillus acidophilus.
3. Clostridium butylicum.
4. Trichoderma polysporum.

Answer: a. Propionibacterium sharmanii.

Question 8. The specific flavour of 'Roquefort cheese' is achieved by ripening it with which of the following?

1. A specific bacterium.
2. A specific fungus.
3. A specific virus.
4. A specific protozoan.

Answer: b. A specific fungus.

Question 9. In industrial production, what is the term used for the very large vessels where microbes are grown on a large scale?

1. Autoclaves.
2. Fermentors.
3. Incubators.
4. Centrifuges.

Answer: b. Fermentors.

Question 10. Which of the following beverages is produced without the process of distillation?

1. Whisky.
2. Brandy.
3. Rum.
4. Wine.

Answer: d. Wine.

Question 11. Brewer's yeast is widely used for fermenting malted cereals and fruit juices to produce which chemical compound?

1. Methanol.
2. Ethanol.
3. Lactic acid.
4. Acetic acid.

Answer: b. Ethanol.

Question 12. What does the Greek term 'antibiotic' literally translate to in the context of disease-causing organisms?

1. Pro-life.
2. Against life.
3. Against bacteria.
4. For health.

Answer: b. Against life.

Question 13. Which antibiotic was the first to be discovered as a chance discovery by Alexander Fleming?

1. Streptomycin.
2. Tetracycline.
3. Penicillin.
4. Erythromycin.

Answer: c. Penicillin.

Question 14. Alexander Fleming discovered Penicillin while working on which of the following bacteria?

1. Streptococcus.
2. Staphylococci.
3. Bacillus.
4. Pseudomonas.

Answer: b. Staphylococci.

Question 15. The full potential of Penicillin as an effective antibiotic was established by which scientists?

1. Watson and Crick.
2. Ernest Chain and Howard Florey.
3. Jacob and Monod.
4. Beadle and Tatum.

Answer: b. Ernest Chain and Howard Florey.

Question 16. In which year were Fleming, Chain, and Florey awarded the Nobel Prize for the discovery of Penicillin?

1928. 1928.
1929. 1940.
1930. 1945.
1931. 1950.

Answer: c. 1945.

Question 17. The disease known as 'kali khansi' in Hindi corresponds to which bacterial disease?

1. Diphtheria.
2. Leprosy.
3. Whooping cough.
4. Plague.

Answer: c. Whooping cough.

Question 18. Which of the following microbes is used for the commercial production of citric acid?

1. Aspergillus niger.
2. Acetobacter aceti.
3. Clostridium butylicum.
4. Lactobacillus.

Answer: a. Aspergillus niger.

Question 19. Acetobacter aceti is a bacterium responsible for the commercial production of which acid?

1. Citric acid.
2. Acetic acid.
3. Butyric acid.
4. Lactic acid.

Answer: b. Acetic acid.

Question 20. Which bacterium is commercially utilized to produce butyric acid?

1. Lactobacillus.
2. Aspergillus niger.
3. Clostridium butylicum.
4. Propionibacterium sharmanii.

Answer: c. Clostridium butylicum.

Question 21. Which enzymes are primarily used in detergent formulations and help in removing oily stains from laundry?

1. Proteases.
2. Pectinases.
3. Lipases.
4. Amylases.

Answer: c. Lipases.

Question 22. Bottled fruit juices bought from the market appear clearer than home-made ones due to the application of which enzymes?

1. Lipases and proteases.
2. Pectinases and proteases.
3. Amylases and ligases.
4. Nucleases and pectinases.

Answer: b. Pectinases and proteases.

Question 23. Streptokinase, modified by genetic engineering, is produced by the bacterium Streptococcus and is used medically for what purpose?

1. As an immunosuppressant.
2. As a clot buster.
3. To lower blood cholesterol.
4. To cure whooping cough.

Answer: b. As a clot buster.

Question 24. Cyclosporin A, an important immunosuppressive agent used in organ transplant patients, is produced by which fungus?

1. Trichoderma polysporum.
2. Monascus purpureus.
3. Penicillium notatum.
4. Aspergillus niger.

Answer: a. Trichoderma polysporum.

Question 25. Statins, which are widely commercialized as blood-cholesterol lowering agents, are produced by which microorganism?

1. Trichoderma polysporum.
2. Monascus purpureus.
3. Saccharomyces cerevisiae.
4. Streptococcus.

Answer: b. Monascus purpureus.

Question 26. How do statins function to lower blood cholesterol levels?

1. By competitively inhibiting the enzyme responsible for cholesterol synthesis.
2. By breaking down cholesterol in the bloodstream.
3. By preventing the absorption of dietary cholesterol in the intestine.
4. By enhancing the excretion of cholesterol through bile.

Answer: a. By competitively inhibiting the enzyme responsible for cholesterol synthesis.

Question 27. Municipal waste-water, containing large amounts of organic matter and microbes, is commonly referred to as what?

1. Effluent.
2. Sludge.
3. Sewage.
4. Flocs.

Answer: c. Sewage.

Question 28. Primary treatment of sewage primarily involves the physical removal of particles through which two processes?

1. Aeration and digestion.
2. Filtration and sedimentation.
3. Chlorination and filtration.
4. Sedimentation and aeration.

Answer: b. Filtration and sedimentation.

Question 29. During primary sewage treatment, floating debris is initially removed by which process?

1. Sequential filtration.
2. Sedimentation.
3. Anaerobic digestion.
4. Flocculation.

Answer: a. Sequential filtration.

Question 30. In primary sewage treatment, all solids that settle at the bottom form what substance?

1. Primary effluent.
2. Activated sludge.
3. Primary sludge.
4. Secondary sludge.

Answer: c. Primary sludge.

Question 31. The primary effluent is passed into large aeration tanks during which stage of sewage treatment?

1. Primary treatment.
2. Secondary treatment.
3. Tertiary treatment.
4. Quaternary treatment.

Answer: b. Secondary treatment.

Question 32. In secondary sewage treatment, what are 'flocs'?

1. Masses of protozoa.
2. Floating debris in primary tanks.
3. Masses of bacteria associated with fungal filaments to form mesh-like structures.
4. Sediments of grit and soil.

Answer: c. Masses of bacteria associated with fungal filaments to form mesh-like structures.

Question 33. The continuous growth of aerobic microbes in the aeration tank significantly reduces which parameter of the effluent?

1. Dissolved oxygen.
2. Biochemical Oxygen Demand (BOD).
3. Salinity.
4. Pathogenic load alone.

Answer: b. Biochemical Oxygen Demand (BOD).

Question 34. What does BOD primarily measure in a water sample?

1. The amount of dissolved inorganic matter.
2. The rate of uptake of oxygen by micro-organisms.
3. The level of heavy metal pollution.
4. The amount of primary sludge present.

Answer: b. The rate of uptake of oxygen by micro-organisms.

Question 35. A greater BOD of waste water indicates what about its polluting potential?

1. It has less polluting potential.
2. It has highly toxic chemicals.
3. It has more polluting potential.
4. It has no organic matter.

Answer: c. It has more polluting potential.

Question 36. Once the BOD of sewage is significantly reduced, the effluent is passed into a settling tank where bacterial flocs sediment. What is this sediment called?

1. Primary sludge.
2. Activated sludge.
3. Anaerobic sludge.
4. Biogas sludge.

Answer: b. Activated sludge.

Question 37. What happens to a small part of the activated sludge in a sewage treatment plant?

1. It is dried and used as fertilizer immediately.
2. It is released into the river.
3. It is pumped back into the aeration tank to serve as an inoculum.
4. It is discarded in landfills.

Answer: c. It is pumped back into the aeration tank to serve as an inoculum.

Question 38. The major part of the activated sludge is pumped into large tanks known as what?

1. Primary settling tanks.
2. Aeration tanks.
3. Anaerobic sludge digesters.
4. Sequential filtration units.

Answer: c. Anaerobic sludge digesters.

Question 39. Which gas is NOT typically a major component of the biogas produced in anaerobic sludge digesters?

1. Methane.
2. Hydrogen sulphide.
3. Carbon dioxide.
4. Oxygen.

Answer: d. Oxygen.

Question 40. Which ministries in India initiated the Ganga Action Plan and Yamuna Action Plan?

1. Ministry of Water Resources.
2. Ministry of Environment and Forests.
3. Ministry of Health and Family Welfare.
4. Ministry of Earth Sciences.

Answer: b. Ministry of Environment and Forests.

Question 41. Biogas predominantly consists of which of the following gases?

1. Carbon dioxide.
2. Hydrogen sulphide.
3. Methane.
4. Carbon monoxide.

Answer: c. Methane.

Question 42. Bacteria that grow anaerobically on cellulosic material and produce large amounts of methane along with CO2 and H2 are collectively called what?

1. Cyanobacteria.
2. Methanogens.
3. Halophiles.
4. Thermoacidophiles.

Answer: b. Methanogens.

Question 43. Which of the following is a common methanogen found in the anaerobic sludge and the rumen of cattle?

1. Methanobacterium.
2. Rhizobium.
3. Azotobacter.
4. Lactobacillus.

Answer: a. Methanobacterium.

Question 44. The excreta of cattle, commonly called gobar, is extremely rich in which type of bacteria?

1. Lactic acid bacteria.
2. Cyanobacteria.
3. Methanogens.
4. Denitrifying bacteria.

Answer: c. Methanogens.

Question 45. A typical biogas plant consists of a concrete tank of what depth where bio-wastes are collected?

1. 5-10 feet.
2. 10-15 feet.
3. 20-25 feet.
4. 30-40 feet.

Answer: b. 10-15 feet.

Question 46. In a biogas plant, what is placed over the slurry that keeps on rising as gas is produced in the tank?

1. A fixed dome.
2. A floating cover.
3. A heavy metal sheet.
4. A plastic mesh.

Answer: b. A floating cover.

Question 47. The spent slurry from a biogas plant may be removed through another outlet and used primarily for what purpose?

1. Cattle feed.
2. Fertiliser.
3. Building material.
4. Water purification.

Answer: b. Fertiliser.

Question 48. The technology of biogas production was developed in India mainly due to the efforts of which organizations?

1. IARI and KVIC.
2. ICAR and CSIR.
3. WHO and UNESCO.
4. ICMR and KVIC.

Answer: a. IARI and KVIC.

Question 49. In agriculture, biocontrol refers to the use of biological methods for controlling what?

1. Plant diseases and pests.
2. Soil erosion.
3. Water usage.
4. Fertiliser application.

Answer: a. Plant diseases and pests.

Question 50. The ladybird beetle is exceptionally useful in controlling which of the following agricultural pests?

1. Mosquitoes.
2. Aphids.
3. Caterpillars.
4. Nematodes.

Answer: b. Aphids.

Question 51. Dragonflies are widely recognized as effective biocontrol agents against which pests?

1. Aphids.
2. Mosquitoes.
3. Bollworms.
4. Beetles.

Answer: b. Mosquitoes.

Question 52. Bacillus thuringiensis (Bt) is used to control which type of insect larvae?

1. Butterfly caterpillars.
2. Aphids.
3. Mosquitoes.
4. Ladybird larvae.

Answer: a. Butterfly caterpillars.

Question 53. How are Bacillus thuringiensis spores typically administered to crops like brassicas and fruit trees?

1. Mixed with water and sprayed onto vulnerable plants.
2. Injected into the plant stems.
3. Mixed into the soil as dry powder.
4. Dispersed into the air as aerosols.

Answer: a. Mixed with water and sprayed onto vulnerable plants.

Question 54. Where is the toxin of Bacillus thuringiensis released to kill the caterpillar?

1. In the respiratory tract of the caterpillar.
2. In the gut of the caterpillar.
3. On the exoskeleton of the caterpillar.
4. In the nervous system of the caterpillar.

Answer: b. In the gut of the caterpillar.

Question 55. Which biological control agent is being developed for use in the treatment of plant disease and is very common in the root ecosystems?

1. Bacillus thuringiensis.
2. Trichoderma species.
3. Monascus purpureus.
4. Agrobacterium tumefaciens.

Answer: b. Trichoderma species.

Question 56. Baculoviruses are excellent candidates for species-specific, narrow spectrum insecticidal applications. Most of these biocontrol agents belong to which genus?

1. Nucleopolyhedrovirus.
2. Retrovirus.
3. Adenovirus.
4. Tobacco mosaic virus.

Answer: a. Nucleopolyhedrovirus.

Question 57. Which of the following statements is true regarding Nucleopolyhedrovirus as a biocontrol agent?

1. They have negative impacts on plants.
2. They are highly effective against target insects but harm non-target insects.
3. They have no negative impacts on plants, mammals, birds, fish, or even non-target insects.
4. They cause diseases in human beings working in fields.

Answer: c. They have no negative impacts on plants, mammals, birds, fish, or even non-target insects.

Question 58. The use of Baculoviruses is highly desirable in programs where beneficial insects are being conserved. What is this comprehensive pest management approach called?

1. Integrated Pest Management (IPM).
2. Intensive Chemical Farming.
3. Organic Monoculture.
4. Biological Amplification.

Answer: a. Integrated Pest Management (IPM).

Question 59. Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi, and which other group?

1. Viruses.
2. Cyanobacteria.
3. Protozoa.
4. Nematodes.

Answer: b. Cyanobacteria.

Question 60. Rhizobium bacteria form symbiotic associations with the roots of which type of plants?

1. Cereal crops.
2. Leguminous plants.
3. Gymnosperms.
4. Bryophytes.

Answer: b. Leguminous plants.

Question 61. Which of the following is a free-living nitrogen-fixing bacterium found in the soil?

1. Rhizobium.
2. Azotobacter.
3. Glomus.
4. Trichoderma.

Answer: b. Azotobacter.

Question 62. Fungi are also known to form symbiotic associations with plants. What is this association called?

1. Lichen.
2. Mycorrhiza.
3. Haustoria.
4. Nodule.

Answer: b. Mycorrhiza.

Question 63. Many members of which fungal genus predominantly form mycorrhiza?

1. Penicillium.
2. Aspergillus.
3. Glomus.
4. Rhizopus.

Answer: c. Glomus.

Question 64. In a mycorrhizal association, what is the primary nutrient that the fungal symbiont absorbs from the soil and passes to the plant?

1. Nitrogen.
2. Phosphorus.
3. Potassium.
4. Calcium.

Answer: b. Phosphorus.

Question 65. Which of the following is NOT a benefit provided to the plant by mycorrhizal associations?

1. Resistance to root-borne pathogens.
2. Tolerance to salinity and drought.
3. Increased absorption of phosphorus.
4. Enhanced carbon dioxide fixation.

Answer: d. Enhanced carbon dioxide fixation.

Question 66. Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments. Which of the following is NOT a nitrogen-fixing cyanobacterium?

1. Anabaena.
2. Nostoc.
3. Oscillatoria.
4. Azospirillum.

Answer: d. Azospirillum.

Question 67. In paddy fields, which group of organisms serves as an important and widely used biofertiliser?

1. Mycorrhizal fungi.
2. Cyanobacteria.
3. Rhizobium.
4. Baculoviruses.

Answer: b. Cyanobacteria.

Question 68. Blue-green algae not only fix nitrogen but also add what to the soil to increase its fertility?

1. Inorganic salts.
2. Organic matter.
3. Synthetic chemicals.
4. Phosphates.

Answer: b. Organic matter.

Question 69. To replenish soil nutrients and reduce dependence on chemical fertilisers, farmers are increasingly switching to which alternative?

1. Biofertilisers.
2. Biopesticides.
3. Synthetic urea.
4. Genetically modified seeds exclusively.

Answer: a. Biofertilisers.

Question 70. When dough is kept overnight for fermentation, it becomes soft and spongy. Which metabolic pathway is primarily responsible for the release of CO2 in this process?

1. Aerobic respiration.
2. Alcoholic fermentation.
3. Lactic acid fermentation.
4. Photophosphorylation.

Answer: b. Alcoholic fermentation.

Question 71. The 'starter' or inoculum added to fresh milk to convert it into curd contains millions of LAB. What critical environmental condition must be met for them to multiply efficiently?

1. Extreme high temperature.
2. Suitable warm temperature.
3. Freezing conditions.
4. High light intensity.

Answer: b. Suitable warm temperature.

Question 72. Which of the following is an accurate match of a microbe and its industrial product?

1. Aspergillus niger - Acetic acid.
2. Acetobacter aceti - Citric acid.
3. Clostridium butylicum - Butyric acid.
4. Lactobacillus - Ethanol.

Answer: c. Clostridium butylicum - Butyric acid.

Question 73. Which type of cheese is known for being ripened by the growth of a specific fungus, giving it a particular flavour?

1. Swiss cheese.
2. Cheddar cheese.
3. Roquefort cheese.
4. Mozzarella cheese.

Answer: c. Roquefort cheese.

Question 74. Which of the following antibiotics was extensively used to treat wounded American soldiers during World War II?

1. Streptomycin.
2. Erythromycin.
3. Penicillin.
4. Tetracycline.

Answer: c. Penicillin.

Question 75. Patients who have undergone myocardial infarction are typically administered which bioactive molecule to remove blood vessel clots?

1. Cyclosporin A.
2. Statins.
3. Streptokinase.
4. Penicillin.

Answer: c. Streptokinase.

Question 76. Statins are competitive inhibitors for the enzyme responsible for the synthesis of which substance in the human body?

1. Glucose.
2. Cholesterol.
3. Proteins.
4. Nucleic acids.

Answer: b. Cholesterol.

Question 77. Which statement accurately describes the effluent from the primary settling tank in a sewage treatment plant?

1. It consists of settled soil and small pebbles.
2. It is free of all dissolved organic matter.
3. It is passed into secondary treatment for biological processing.
4. It consists primarily of anaerobic bacteria.

Answer: c. It is passed into secondary treatment for biological processing.

Question 78. What happens to the Biochemical Oxygen Demand (BOD) of the sewage as useful aerobic microbes consume the major part of its organic matter?

1. It increases significantly.
2. It decreases significantly.
3. It remains unchanged.
4. It becomes zero instantly.

Answer: b. It decreases significantly.

Question 79. Activated sludge, formed during secondary sewage treatment, is primarily composed of what?

1. Sedimented floating debris.
2. Sedimented bacterial flocs.
3. Inorganic grit and pebbles.
4. Pathogenic viruses.

Answer: b. Sedimented bacterial flocs.

Question 80. During anaerobic sludge digestion in sewage treatment, a mixture of gases is produced. This mixture is commonly known as what?

1. Natural gas.
2. Biogas.
3. Greenhouse gas.
4. Syngas.

Answer: b. Biogas.

Question 81. Why can untreated sewage not be discharged directly into natural water bodies like rivers?

1. It is rich in oxygen.
2. It contains large amounts of organic matter and pathogenic microbes.
3. It reduces the water temperature.
4. It contains heavy metals only.

Answer: b. It contains large amounts of organic matter and pathogenic microbes.

Question 82. Which of the following is true about methanogens?

1. They are strictly aerobic bacteria.
2. They break down cellulosic material anaerobically.
3. They are the primary agents of alcoholic fermentation.
4. They cause lethal diseases in cattle.

Answer: b. They break down cellulosic material anaerobically.

Question 83. The rumen of cattle is home to methanogens. What vital role do these bacteria play for the cattle?

1. They synthesize vitamins.
2. They help in the breakdown of cellulose.
3. They digest proteins.
4. They protect against viral infections.

Answer: b. They help in the breakdown of cellulose.

Question 84. The Ministry of Environment and Forests initiated the Ganga and Yamuna Action Plans primarily to propose the building of what?

1. Hydroelectric dams.
2. A large number of sewage treatment plants.
3. Biogas plants.
4. Industrial effluent outlets.

Answer: b. A large number of sewage treatment plants.

Question 85. The biological control of agricultural pests and diseases is based on natural processes of what ecological interaction?

1. Commensalism.
2. Mutualism.
3. Predation.
4. Amensalism.

Answer: c. Predation.

Question 86. Which method of pest control heavily relies on toxic chemicals that are harmful to human beings, animals, and the environment?

1. Biocontrol.
2. Conventional chemical agriculture.
3. Integrated Pest Management.
4. Organic farming.

Answer: b. Conventional chemical agriculture.

Question 87. The belief behind organic farming regarding pest management is that eradication of pests is not only impossible but also what?

1. Economically viable.
2. Undesirable, as it disrupts food chains.
3. Necessary for high yields.
4. Required for plant health.

Answer: b. Undesirable, as it disrupts food chains.

Question 88. In Integrated Pest Management (IPM), Baculoviruses of the genus Nucleopolyhedrovirus are preferred because of their what?

1. Broad-spectrum insecticidal applications.
2. Ability to kill all insects in the field.
3. Species-specific, narrow spectrum insecticidal applications.
4. Persistence in the soil for decades.

Answer: c. Species-specific, narrow spectrum insecticidal applications.

Question 89. Which fungal biocontrol agent is particularly effective against several plant pathogens in the root ecosystem?

1. Penicillium.
2. Rhizopus.
3. Trichoderma.
4. Mucor.

Answer: c. Trichoderma.

Question 90. Genetically modified crop plants, such as Bt cotton, have incorporated the toxic genes of which bacterium?

1. Agrobacterium tumefaciens.
2. Bacillus thuringiensis.
3. Rhizobium leguminosarum.
4. Pseudomonas putida.

Answer: b. Bacillus thuringiensis.

Question 91. Azospirillum and Azotobacter are examples of what type of organisms?

1. Symbiotic nitrogen-fixing bacteria.
2. Free-living nitrogen-fixing bacteria.
3. Nitrogen-fixing cyanobacteria.
4. Mycorrhizal fungi.

Answer: b. Free-living nitrogen-fixing bacteria.

Question 92. Cyanobacteria serve as an important biofertiliser because they possess the ability to do what?

1. Solubilize soil phosphorus.
2. Fix atmospheric nitrogen.
3. Break down complex lignin.
4. Produce insecticidal toxins.

Answer: b. Fix atmospheric nitrogen.

Question 93. A student observing a drop of curd under a microscope is likely to see millions of which microbe?

1. Saccharomyces.
2. Lactobacillus.
3. Aspergillus.
4. Penicillium.

Answer: b. Lactobacillus.

Question 94. The continuous use of chemical fertilisers in agriculture has led to which major environmental problem?

1. Ozone depletion.
2. Environmental pollution.
3. Acid rain exclusively.
4. Deforestation.

Answer: b. Environmental pollution.

Question 95. In modern agriculture, what is being promoted as a sustainable and eco-friendly alternative to chemical fertilisers?

1. Synthetic pesticides.
2. Biofertilisers.
3. High yielding varieties without fertilizers.
4. Heavy machinery.

Answer: b. Biofertilisers.

Question 96. What is the fundamental difference between the primary and secondary stages of sewage treatment?

1. Primary is biological, secondary is mechanical.
2. Primary is mechanical, secondary is biological.
3. Primary involves chlorination, secondary involves sedimentation.
4. Both are purely mechanical processes.

Answer: b. Primary is mechanical, secondary is biological.

Question 97. Which of the following microbes has NOT been widely used in the production of traditional foods by fermentation?

1. Bacteria.
2. Viruses.
3. Yeast.
4. Fungi.

Answer: b. Viruses.

Question 98. Microbes are utilized to ferment which of the following foods commonly used in East Asian cuisine?

1. Bamboo shoots and soybean.
2. Apples and oranges.
3. Wheat and barley only.
4. Coffee and cocoa.

Answer: a. Bamboo shoots and soybean.

Question 99. The discovery of which life-saving chemicals is regarded as one of the most significant discoveries of the twentieth century?

1. Biofertilisers.
2. Antibiotics.
3. Monoclonal antibodies.
4. Recombinant proteins.

Answer: b. Antibiotics.

Question 100. In addition to primary and secondary treatments, what is the third step of sewage treatment (tertiary treatment) generally meant for, though not extensively detailed in basic NCERT?

1. Removing floating debris.
2. Reducing BOD.
3. Making water suitable for drinking via advanced chemical/physical methods.
4. Digesting activated sludge.

Answer: c. Making water suitable for drinking via advanced chemical/physical methods.

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