31. Acid rain damages:
A) Buildings
B) Plants
C) Soil
D) All
Answer: D
32. Which process purifies water naturally?
A) Distillation
B) Filtration
C) Water cycle
D) Evaporation
Answer: C
33. Which layer is closest to Earth?
A) Troposphere
B) Stratosphere
C) Mesosphere
D) Thermosphere
Answer: A
34. The major source of CO₂ is:
A) Respiration
B) Combustion
C) Photosynthesis
D) Evaporation
Answer: B
35. Deforestation causes:
A) Cooling
B) More oxygen
C) Global warming
D) Rainfall increase
Answer: C
36. Recycling helps to:
A) Increase waste
B) Reduce pollution
C) Waste energy
D) None
Answer: B
37. Which pollutant causes respiratory problems?
A) SO₂
B) O₂
C) N₂
D) He
Answer: A
38. The main source of water pollution is:
A) Rain
B) Sewage
C) Sunlight
D) Oxygen
Answer: B
39. Which gas is essential for respiration?
A) CO₂
B) O₂
C) N₂
D) CH₄
Answer: B
40. Which energy is clean?
A) Coal
B) Oil
C) Solar
D) Gas
Answer: C