Assertion (A): The thickness of the lithosphere is very fragile compared to the nature and composition of the earth.

Reason (R): There are continuous changes in the earth's crust due to forces of nature.

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.

What life sustaining unit contains only one per cent of the earth's mass?

1. biosphere
2. lithosphere
3. crust
4. mantle

Extending upwards, the earth is enveloped by a blanket of gases. Name it.

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

The diameter of the core is about …………… km.

1. 5000
2. 6000
3. 7000
4. 8000