Ozone is a very toxic gas and a strong oxidizing agent. It is still useful for life on earth :

1. because it traps harmful UV-rays.

2. because it balances global warming.

3. because it traps harmful X-rays.

4. because it  traps harmful $\mathrm{\gamma }$-rays.

Pollution that occurs in the lowest layer of the atmosphere is :

1. Stratosphere pollution.

2. Ozone layer pollution.

3. Air pollution.

4. Troposphere pollution.

The phenomenon in which atmospheric gases trap the heat radiations from the sun near the earth’s surface and keeps it warm is known as-

1. Natural greenhouse effect

2. Tyndall effect

3. Heating effect

4. Joule’s effect

The main air pollutant among the following is : 

1. CO

2. $C{O}_2$

3. $N_2$

4. Sulphur

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

An increase in ${\mathrm{CO}}_2$ concentration in the atmosphere will result in : 

1. Adverse effects on natural vegetation.

2. Global warming.

3. Temperature decrease in a global atmosphere.

4. Genetic disorders in plants and animals.

The most harmful air pollutant produced by automobiles is- 

1. ${\mathrm{HNO}}_2$

2. NO

3. ${\mathrm{SO}}_2$

4. CO

The incorrect statement about carbon monoxide is-

A non-greenhouse gas is : 
1. CO₂
2. CH₄
3. Chlorofluorocarbons
4. O₂