Choose the right option.

1. Melting of polar ice caps is taking place due to
   1. global warming
   2. rise in salinity of the sea
   3. drying up of rivers
2. Global warming will lead to
   1. increase in the density of air
   2. change in the ions of the ionosphere
   3. cyclones and hurricanes in coastal areas
3. The main objective of the Montreal Protocol was
   1. to increase global forest cover
   2. to reduce pollution of water bodies
   3. to lower the production of Ozone Depleting Substances
4. The ozone layer helps in
   1. preventing the ultraviolet rays from reaching the Earth
   2. preserving the optimum temperature of the Earth
   3. absorbing the polluting gases released by the Earth

Give one term for each of the following.

1. The gas that occupies the maximum volume of the stratosphere.
2. The upper limit of the troposphere that separates it from the stratosphere.
3. The coldest layer of the atmosphere.
4. A fossil fuel that contributes to global warming.
5. The hottest layer of the atmosphere.
6. The continent over which a large ozone hole has developed.
7. Harmful rays that lead to cataract and skin cancer in human beings.

All changes in weather conditions occur in the troposphere. Give reasons.

The troposphere protects the Earth from extremes of temperature. Give reasons.

Stratosphere provides ideal flying conditions for aircraft. Give reasons.