Choose the correct alternative from the following : - Assertion (A) : Most of the ancient civilisations grew near the rivers.
Reason (R) : The main occupation of man was agriculture.

B. BOTH A AND R ARE TRUE BUT R IS NOT THE CORRECT EXPLANATION OF A.

Choose the correct alternative from the following : - Assertion (A) : Earthworms are not good for agriculture.
Reason (R) : Earthworms break down the soil into fine particles and make it soft.

D. A IS FALSE BUT R IS TRUE.

Choose the correct alternative from the following : - Assertion (A) : There is no vaccine for AIDS.
Reason (R) : The AIDS virus changes its genetic code.

A. BOTH A AND R ARE TRUE AND R IS THE CORRECT EXPLANATION OF A.

Choose the correct alternative from the following : - Assertion (A) : Downpour of rain lessens the humidity in the atmosphere.
Reason (R) : Rains are caused when atmosphere cannot hold more moisture.

D. A IS FALSE BUT R IS TRUE.

Choose the correct alternative from the following : - Assertion (A) : Red colour  of blood is due to haemoglobin.
Reason (R) : Haemoglobin is a red pigment.

A. BOTH A AND R ARE TRUE AND R IS THE CORRECT EXPLANATION OF A.