A is father of B. C is wife of D. E is son of C. B is sister of E.
How is D related to A?
I. Son
II. Brother
III. Father
IV. Son-in-law

Question: 以下哪项是正确的？
Options:
A. 仅 IV, B. 仅 II, C. 仅 III, D. 仅 I
Answer: A
True statement: IV