The ozone layer of the upper atmosphere is being destroyed by : 

1. Sulphur dioxide

2. Carbon dioxide

3. Chlorofluorocarbon

4. Smog

Most hazardous metal pollutant of automobile exhaust is

(1) Hg

(2) Cd

(3) Pb

(4) Cu

$S{O}_2$ pollution is indicated by

1. Grasses

2. Mosses

3. Lichens

4. Fossils

B.O.D is connected with

(1) Organic matter

(2) Microbes

(3) Both

(4) None

Acid rain is due to an increase in the atmospheric concentration of : 

1. Ozone, and dust

2. $C{O}_{\mathrm{2,}}$ and CO

3. $S{O}_{\mathrm{3,}}$ and CO

4 $S{O}_{\mathrm{2,}}$ and $N{O}_2$

Soil erosion is greater when

(1) No rain occurs

(2) Winds do not blow

(3) The rainfall is evenly distributed

(4) The Rainfall is received in heavy down pour

Soil erosion can be prevented by : 

1. Overgrazing

2. Removal of vegetation

3. Afforestation (Plantation)

4. Increasing bird population

Soil conservation is the process where

1. Soil is aerated

2. Soil erosion is allowed

3. Soil is protected against loss

4. Sterile soil is converted into fertile soil

... is not a greenhouse gas :-
1. Hydrogen
2. Carbon dioxide
3. Methane
4. Nitrous oxide or $N_{2}O$

The concentration of Peroxy Acetyl Nitrate (PAN) maximum in:-

(1) Fog

(2) Smoke

(3) Smog

(4) Photochemical smog