Assertion (A) : Human female has a perfect pair of sex chromosome.
Reason (R) : Sex chromosome contributed by the human male in the zygote decides the sex of a child.
Generated by claude-sonnet-4-6 · 2026-06-15 06:54 · grounding rag
Model Answer
(D) (A) is false, but (R) is true.
Human female has a perfect pair of sex chromosomes (XX) — this is true, so (A) is actually true. Wait — re-reading: (A) states the female has a perfect pair, which is correct. The sex chromosome contributed by the father (X or Y) determines the sex of the child — (R) is also true. However, (R) does not explain (A); both are independent facts.
Answer: (B) — Both (A) and (R) are true, but (R) is not the correct explanation of (A).
Source: Chapter 8, Section 8.2.4 – Sex Determination
---
Explanation
- (A) is TRUE: The textbook clearly states "Women have a perfect pair of sex chromosomes, both called X."
- (R) is TRUE: "The sex of the children will be determined by what they inherit from their father."
- But (R) explains sex determination, not why females have a perfect pair — so (R) does not explain (A). Hence (B) is correct.
- Common mistake: Students may choose (A), confusing "correct explanation" with just "both being true."