Assertion (A): The concentration of harmful chemicals is more in human beings.
Reason (R): Man is at the apex of the food chain.
Harmful chemicals accumulate progressively through each trophic level in the food chain. Since man is at the apex of every food chain, the concentration of harmful chemicals is most in humans.
- Assertion is true.
- Reason is true.
- Reason is the correct explanation of assertion.
So, the correct answer is (a).