Mountain climbers set up camps at the base as well as at regular intervals along their climb. Why?

1. To acclimatize their bodies to lower concentration of air.
2. To acclimatize their bodies to lower temperature.
3. To acclimatize their bodies to pressure.
4. All of the above.

Assertion (A): The atmosphere is the most dynamic entity on the earth's surface.

Reason (R): Large masses of air are being moved up and down and across the surface of the earth.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R does not explain A.
3. A is true but R is false.
4. A is false but R is true.

Which amongst the following is not a domain of the Biosphere?

1. Lithosphere
2. Exosphere
3. Hydrosphere
4. Atmosphere

………….. extends up to a height of about 400 km and is responsible for enabling radio communication.

1. Mesosphere
2. Ionosphere
3. Stratosphere
4. Troposphere