Effects of Global Warming

Q. Which of the following are true regarding ${\text{CO}}_2$?

a. Excess of ${\text{CO}}_2$ acts as a pollutant
b. Plants take in ${\text{CO}}_2$ for photosynthesis
c. Deforestation leads to decrease in the amount of ${\text{CO}}_2$ in air
d. Less quantity of ${\text{CO}}_2$ causes rise in temperature

1. a and b

2. a, b and d

3. b and c

4. a, b and c