The gases which cause acid rain are:

1. sulphur dioxide and oxygen
2. nitrogen and oxygen
3. carbon dioxide and water vapour
4. nitrogen dioxide and sulphur dioxide.

Which of the following is not a greenhouse gas?

1. Carbon dioxide
2. Sulphur dioxide
3. Methane
4. Nitrous oxide

The gas responsible for ozone depletion is:

1. oxygen
2. chlorofluorocarbons
3. carbon dioxide
4. sulphur dioxide

Fill in the blanks:

(a) The layer of air around the earth is called the …………… .

(b) Although we cannot see air, we can …………… it.

(c) Air is a …………… of gases.

(d) Plants and animals maintain the balance of …………… and …………… in air.

(e) Polluted air is …………… for health.

(f) The supporter of combustion in air is …………… .

(g) Green plants need …………… to prepare food.

(h) Oxygen is used in …………… of the food to get …………… .

(i) Aquatic plants and animals use …………… in water.

(j) The reddish brown powder on the surface of iron nails exposed to air and moisture is called …………… .