What is the temperature variation in the mantle in °C?

1. 1500 to 3700
2. 1500 to 2500
3. 1000 to 3700
4. 1000 to 4000

Name the mantle-core interface where primary seismic waves slow down and secondary seismic waves disappear completely.

1. Gutenberg Discontinuity
2. Mantlic Discontinuity
3. Core Discontinuity
4. Mohorovicic Discontinuity

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