11. High BOD indicates:
A) Clean water
B) Polluted water
C) Neutral water
D) Pure water
Answer: B
12. Which layer contains ozone?
A) Troposphere
B) Stratosphere
C) Mesosphere
D) Thermosphere
Answer: B
13. Photochemical smog is formed due to:
A) CO₂
B) Sunlight and pollutants
C) Oxygen
D) Hydrogen
Answer: B
14. Primary pollutants are:
A) Formed in atmosphere
B) Directly emitted
C) Secondary
D) None
Answer: B
15. Secondary pollutants are formed by:
A) Direct emission
B) Chemical reactions
C) Plants
D) Animals
Answer: B
16. Which gas causes ozone depletion?
A) CO₂
B) CFCs
C) O₂
D) N₂
Answer: B
17. CFC stands for:
A) Chlorofluorocarbon
B) Carbon Fluoride
C) Chlorine Carbon
D) None
Answer: A
18. Eutrophication is due to:
A) Lack of nutrients
B) Excess nutrients
C) Oxygen
D) Nitrogen gas
Answer: B
19. Which pollutant causes acid rain?
A) SO₂
B) O₂
C) H₂
D) N₂
Answer: A
20. Noise pollution is measured in:
A) Watts
B) Decibels
C) Hertz
D) Joules
Answer: B