Introducing a man, a woman said, “He is the only son of the mother of my mother.” How is the woman related to the man?

The correct answer is D. Maternal aunt.

The woman’s mother has a mother, who is the man’s grandmother. The man is the only son of his grandmother, so he is the woman’s first cousin. The woman’s mother is the man’s aunt, so the woman is the man’s maternal aunt.

Option A is incorrect because the woman is not the man’s mother. Option B is incorrect because the woman is not the man’s sister. Option C is incorrect because the woman is not the man’s niece.