3871: The half-life of a radio active element is 5 years. The fraction of the radioactive substance that remains after 20 years is
(a) 1/2
(b) 1/4
(c) 1/8
(d) 1/16
3872: In terms of value, which one of the following commodities accounted for the largest agricultural exports by India during the three year period from 1997- 1998 to 1999-2000?
(a) Cereals
(b) Marine products
(c) Spices
(d) Tea
3873: What is the role of ultraviolet (UV) radiation in the water purification systems?
1. It inactivates/kills the harmful micro-organism in water.
2. It removes all the undesirable odours from the water.
3. It quickens the sedimentation of solid particles, removes turbidity and improves the clarity of water.
Which of the statements given above is/are correct?
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
3874: Assertion (A):
Harshavardhana convened the Prayag Assembly.
Reason (R):
He wanted to popularise only the Mahayana form of Buddhism.
(a) Both A and R are individually true, and R is the correct explanation of A
(b) Both A and R are individually true, but R is NOT a correct explanation of A
(c) A is true, but R is false
(d) A is fasle, but R is true
3875: Assertion
Great Britain gave India her independence on August 15, 1947.
Reason :
Great Britain became weak after her involvement in World War II.
(a) both A and R are true but R is not the reason for A
(b) both A and R are true but R is the reason for A
(c) neither A nor R is correct
(d) A is correct but R is wrong