Without green house effect, the average temperature of earth’s surface would have been —

1. -18°C
2. 33°C
3. 0°C
4. 15°C

Global warming means a …………… in average effective temperature near the earth’s surface due to an …………… in the amount of greenhouse gases in its atmosphere.

1. decrease, increase
2. decreases, decrease
3. increase, decrease
4. increase, increase

Assertion (A) : Fishes survive in ponds even when the atmospheric temperature is below 0°C.

Reason (R) : The anomalous expansion of water helps in preserving aquatic life.

1. both A and R are true and R is the correct explanation of A
2. both A and R are true and R is not the correct explanation of A
3. assertion is false but reason is true
4. assertion is true but reason is false

What do you mean by green house effect?