II. Encircle the letter of the correct answer.
1. Which of the following describes the homosphere?
a. In this region, auroras are formed.
b. In this region, there is no mixing of gases.
C. In this region, gases tend to separate in layers.
d. In this region, there is continuous movement of air masses.
2. Why are carbon dioxide and water vapor called as greenhouse gases?
a. They absorb heat and prevent it from escaping to the outer space.
b. They release heat and prevent it from escaping to the outer space.
C. They absorb heat and prevent it from escaping to the earth's surface.
d. None of these.
3. Which of the following gases is most abundant in the Earth's atmosphere?
a. Carbon dioxide
C. Nitrogen
b. Hydrogen
d. Oxygen​