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.

Which, of the following, gases contributes  nearly 50 % to the green house effect (which, in turn, causes global warming) ?

1. SO₂

2. SO₃

3. CO₂

4. Water vapour

Green plants use carbon dioxide for photosynthesis and return oxygen to the atmosphere. Even then carbon dioxide is considered to be responsible for green house effect : 

1. Due to an increase in atmospheric temperature.

2. Due to ozone depletion.

3. Due to decrease in atmospheric temperature.

4. Due to an increase in chlorophyll concentration.

The most hazardous metal pollutant of automobile exhaust is : 

1. Hg

2. Cd

3. Pb

4. Cu

The oxygen present today in the atmosphere- 

1. Is a plant product.

2. Came from ozone.

3. Was present in the beginning.

4. Is produced by carbon dioxide.

The most harmful air pollutant produced by automobiles is- 

1. ${\mathrm{HNO}}_2$

2. NO

3. ${\mathrm{SO}}_2$

4. CO