Same type of question: what is the central idea in the paragraphs
- Words: but (l. 1), But (l. 4), So...that (l. 6).
- C has the word procreation, not really what the text is about.
- D is about the male physique, not mentioned.
The first but (l.1) signals that the Y-chromosone is 'losing'. The second But (l. 4) signals that the chromosone isn't what it used to be.
There is a change over time, therefore A is the correct answer.