Why does an author use dialogue in characterization

The answer is 'A'.

Hope this helps!!

The correct answer is C. The metaphor portrays Polonius as foolish and weak.

Explanation:

Just read the excerpt - Hamlet compares Polonius to a 'great baby [...] not yet out of his swaddling-clouts.' Obviously, when a grown man is compared to a baby, that's not a positive thing, which is why A and B are incorrect. There is no indication that Polonius is angry or mean.

This is why C is correct here.