Nature’s Treasures Part 4: MCQs (Q76–Q100)

Part IV — Questions 76–100

76. Which soil layer contains retained water and plant roots mainly?
    A. Bedrock
    B. Topsoil
    C. Parent rock
    D. Solid rock layer
    Correct Answer: B — Topsoil
    Explanation:
    A: Bedrock is beneath soil layers.
    B: Correct — topsoil has organic matter, nutrients and roots.
    C: Parent rock is the material from which soil develops but not where roots mainly sit.
    D: Solid rock is not suitable for root growth.

77. Which of the following can be used to produce biogas?
    A. Plastic waste only
    B. Animal dung and organic waste
    C. Glass bottles
    D. Metal scrap
    Correct Answer: B — Animal dung and organic waste
    Explanation:
    A: Plastics are not biodegradable feedstock for biogas.
    B: Correct — anaerobic digestion of organic waste produces biogas (methane).
    C: Glass is inert and not used for biogas production.
    D: Metal does not produce biogas.

78. Which of the following is a major component of soil?
    A. Oxygen only
    B. Mineral particles, organic matter, air and water
    C. Pure water only
    D. Only living plants
    Correct Answer: B — Mineral particles, organic matter, air and water
    Explanation:
    A: Soil includes oxygen but many more components.
    B: Correct — soil is a mixture of mineral particles (sand, silt, clay), organic matter, water and air.
    C: Pure water is not soil.
    D: Living plants are part of the ecosystem but not the main constituents.

79. Which of the following is a way to prevent water pollution?
    A. Dumping industrial waste into rivers
    B. Treating sewage before releasing it into water bodies
    C. Throwing plastics into lakes
    D. Using harmful pesticides near waterways
    Correct Answer: B — Treating sewage before releasing it into water bodies
    Explanation:
    A: Dumping industrial waste pollutes water.
    B: Correct — treatment reduces contaminants entering water systems.
    C: Plastics pollute lakes and harm aquatic life.
    D: Pesticides runoff causes water pollution and eutrophication.

80. Why should we conserve natural resources?
    A. They are unlimited
    B. We can create them instantly when used up
    C. They are limited and essential for life and future generations
    D. To increase pollution
    Correct Answer: C — They are limited and essential for life and future generations
    Explanation:
    A: Many resources are limited and cannot be replaced quickly.
    B: Some resources take millions of years to form and cannot be created instantly.
    C: Correct — conservation ensures availability for current and future needs.
    D: Conservation aims to reduce pollution, not increase it.

81. Which of these is a non-metal widely used as fertilizer (compound containing it)?
    A. Iron
    B. Nitrogen (in compounds like ammonium nitrate)
    C. Copper
    D. Gold
    Correct Answer: B — Nitrogen (in compounds like ammonium nitrate)
    Explanation:
    A: Iron is a metal used in industry, not the main fertilizer element here.
    B: Correct — nitrogen is a key plant nutrient widely used in fertilizers.
    C: Copper is a trace element, not a major fertilizer component.
    D: Gold is not used in fertilizers.

82. Which of the following is used to identify soil type in the field quickly?
    A. Colour, texture and feel test
    B. Smell only
    C. Taste the soil
    D. Guess randomly
    Correct Answer: A — Colour, texture and feel test
    Explanation:
    A: Correct — farmers test soil by feeling and observing colour and texture to infer properties.
    B: Smell can give clues but is not sufficient alone.
    C: Tasting soil is unsafe and not recommended.
    D: Random guesses are not reliable.

83. Which of the following is a sustainable agricultural practice?
    A. Continuous monoculture with heavy chemical use
    B. Crop rotation and organic farming
    C. Removing all cover crops
    D. Excessive tilling only
    Correct Answer: B — Crop rotation and organic farming
    Explanation:
    A: Continuous monoculture and heavy chemicals degrade soil health.
    B: Correct — crop rotation prevents nutrient depletion and organic farming reduces chemical use.
    C: Cover crops protect and enrich soil; removing them is harmful.
    D: Excessive tilling increases erosion and soil disturbance.

84. Which of these energy sources relies on heat from Earth?
    A. Solar energy
    B. Wind energy
    C. Geothermal energy
    D. Hydropower
    Correct Answer: C — Geothermal energy
    Explanation:
    A: Solar is from sunlight.
    B: Wind is atmospheric.
    C: Correct — geothermal taps Earth’s internal heat for energy.
    D: Hydropower uses water flow, not Earth’s internal heat.

85. Which of the following is an effect of oil drilling on coastal ecosystems?
    A. Nothing, no effect at all
    B. Habitat destruction, oil spills harming marine life
    C. Immediate improvement of water quality
    D. Increase in native plant regeneration always
    Correct Answer: B — Habitat destruction, oil spills harming marine life
    Explanation:
    A: Drilling has environmental impacts.
    B: Correct — spills and infrastructure disrupt habitats and wildlife.
    C: Drilling typically harms rather than improves water quality.
    D: Native plants often decline due to disturbance.

86. Which among the following keeps the atmosphere clean by reducing dust and other particles?
    A. Planting urban trees and maintaining vegetation
    B. Burning garbage openly
    C. Increased vehicular emissions only
    D. Cutting down roadside trees
    Correct Answer: A — Planting urban trees and maintaining vegetation
    Explanation:
    A: Correct — vegetation traps dust particles and improves air quality.
    B: Burning garbage creates more pollutants.
    C: More vehicles increase emissions and worsen air quality.
    D: Cutting trees reduces their cleansing effect.

87. Which of the following can be used to reduce household energy consumption?
    A. Keep all electrical appliances on standby always
    B. Use energy-efficient bulbs and switch off unused appliances
    C. Leave lights on during daytime unnecessarily
    D. Overuse water heaters continuously
    Correct Answer: B — Use energy-efficient bulbs and switch off unused appliances
    Explanation:
    A: Standby consumes energy; turning off saves more.
    B: Correct — efficient bulbs and switching off save electricity.
    C: Unnecessary lights waste energy.
    D: Overusing heaters wastes energy.

88. Which of these is a main reason why wetlands are important?
    A. They are good places to dump waste
    B. They act as natural water filters and support biodiversity
    C. They cause flooding everywhere always
    D. They remove forests permanently
    Correct Answer: B — They act as natural water filters and support biodiversity
    Explanation:
    A: Dumping waste harms wetlands; not a reason for their importance.
    B: Correct — wetlands filter pollutants, store floodwater and support diverse life.
    C: Wetlands can reduce flood impacts by storing water.
    D: Wetlands are rich ecosystems, not forest removers.

89. Which of the following is true about composting?
    A. It turns organic waste into nutrient-rich soil amendment
    B. It turns plastic into soil
    C. It causes soil to lose fertility
    D. It requires burning organic matter
    Correct Answer: A — It turns organic waste into nutrient-rich soil amendment
    Explanation:
    A: Correct — composting decomposes organic waste into humus that enriches soil.
    B: Plastics do not compost into soil.
    C: Compost improves, not reduces, soil fertility.
    D: Composting is a biological process, not burning.

90. Which action would most help conserve marine life?
    A. Throwing non-biodegradable waste into seas
    B. Overfishing to increase profits
    C. Reducing plastic use and preventing oil spills
    D. Polluting rivers that lead to ocean
    Correct Answer: C — Reducing plastic use and preventing oil spills
    Explanation:
    A: Dumping waste harms marine organisms.
    B: Overfishing reduces populations and harms ecosystems.
    C: Correct — reducing plastics and spills protects marine habitats and species.
    D: Polluting rivers carries contaminants to oceans.

91. Which of these is NOT a reason to save forests?
    A. To maintain biodiversity
    B. To regulate climate and rainfall
    C. To increase soil erosion
    D. To supply wood and other forest products sustainably
    Correct Answer: C — To increase soil erosion
    Explanation:
    A: Forests support many species — reason to save them.
    B: Forests influence climate — reason to conserve.
    C: Correct — increasing erosion is a negative consequence, not a reason.
    D: Sustainable use of forest products supports livelihoods.

92. Which of the following is a consequence of desertification?
    A. Increased arable land everywhere
    B. Loss of productive land and vegetation
    C. More rainfall in desert areas always
    D. Growth of forests spontaneously
    Correct Answer: B — Loss of productive land and vegetation
    Explanation:
    A: Desertification reduces arable land, not increase it.
    B: Correct — land becomes less productive and vegetation declines.
    C: Desertification generally reduces vegetation and does not increase rainfall.
    D: Forests do not grow spontaneously in desertified areas.

93. Which of these is a sustainable way to use forest products?
    A. Clear-cutting entire forest for timber without replanting
    B. Selective logging with replanting and community forestry
    C. Allowing illegal logging and trade
    D. Burning forest debris indiscriminately
    Correct Answer: B — Selective logging with replanting and community forestry
    Explanation:
    A: Clear-cutting destroys ecosystems and is unsustainable.
    B: Correct — selective logging, replanting and involving local communities supports sustainability.
    C: Illegal logging undermines conservation.
    D: Burning debris can release pollutants and harm regeneration.

94. Which of these is a common pollutant from vehicles?
    A. Oxygen
    B. Carbon monoxide and particulate matter
    C. Water vapour only (harmless)
    D. Pure nitrogen only (harmless)
    Correct Answer: B — Carbon monoxide and particulate matter
    Explanation:
    A: Oxygen is not a pollutant from vehicles.
    B: Correct — incomplete combustion produces CO and particulates harmful to health.
    C: Vehicles do emit some water vapour but also harmful gases; water alone is not the full answer.
    D: Nitrogen is abundant in air but vehicle emissions include NOx which are pollutants.

95. Which of the following helps maintain soil fertility naturally?
    A. Continuous monoculture without rest
    B. Adding compost and crop rotation
    C. Removing organic matter always
    D. Excessive use of chemical pesticides only
    Correct Answer: B — Adding compost and crop rotation
    Explanation:
    A: Continuous monoculture depletes nutrients.
    B: Correct — compost adds nutrients and rotation prevents nutrient depletion and pests.
    C: Removing organic matter reduces soil quality.
    D: Excessive pesticides harm beneficial organisms and soil health.

96. Which of these is an example of a metallic mineral?
    A. Coal
    B. Copper
    C. Rock salt
    D. Limestone
    Correct Answer: B — Copper
    Explanation:
    A: Coal is a fossil fuel, not a metal.
    B: Correct — copper is a metal used in wiring and plumbing.
    C: Rock salt is non-metallic mineral.
    D: Limestone is a sedimentary rock used in construction.

97. Which of the following is the correct sequence in the water cycle?
    A. Evaporation → Condensation → Precipitation → Collection
    B. Precipitation → Evaporation → Collection → Condensation
    C. Condensation → Collection → Evaporation → Precipitation
    D. Evaporation → Condensation → Precipitation → Collection
    Correct Answer: D — Evaporation → Condensation → Precipitation → Collection
    Explanation:
    A: Correct — water evaporates, forms clouds (condensation), falls as precipitation and collects in bodies.
    B: Incorrect order.
    C: Incorrect order.
    D: Same as A; correct sequence described.

98. Which of the following is a practice that reduces river pollution?
    A. Discharging untreated industrial effluents into rivers
    B. Setting up sewage treatment and stopping dumping of wastes
    C. Throwing plastics and chemicals into rivers
    D. Allowing runoff from farms containing pesticides to flow unchecked
    Correct Answer: B — Setting up sewage treatment and stopping dumping of wastes
    Explanation:
    A: Discharging untreated effluents pollutes rivers.
    B: Correct — treatment and prevention reduce contamination significantly.
    C: Dumping plastics and chemicals causes pollution.
    D: Agricultural runoff needs management to reduce pollutants.

99. Which of the following is true about coral reefs?
    A. They are formed by rocks only and have no living organisms
    B. They are diverse ecosystems formed by corals and support many marine species
    C. They grow quickly overnight
    D. They are not affected by water pollution
    Correct Answer: B — They are diverse ecosystems formed by corals and support many marine species
    Explanation:
    A: Coral reefs are living structures built by coral animals (polyps) and algae.
    B: Correct — reefs host high biodiversity and provide ecosystem services.
    C: Reefs grow slowly over long periods, not overnight.
    D: Reefs are highly sensitive to pollution and climate change.

100. What is the best description of sustainable development?
     A. Using resources quickly without thinking of future needs
     B. Meeting present needs without compromising ability of future generations to meet theirs
     C. Consuming as much as possible for short-term gain
     D. Destroying habitats for immediate industrial benefit
     Correct Answer: B — Meeting present needs without compromising ability of future generations to meet theirs
     Explanation:
     A: That describes unsustainable use, not sustainable development.
     B: Correct — sustainable development balances present and future needs.
     C: Short-term overconsumption is unsustainable.
     D: Habitat destruction undermines sustainability.

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