Pointing to a photograph, a man said, "I have no brother or sister but that man's father is my father's son."
Whose photograph was it ?

A. His own
B. His son's
C. His father's
D. His nephew's
E. None of these
Answer: B . His son's


Since the narrator has no brother, his father's son is he himself.
So, the man who is talking is the father of the man in the photograph or the man in the photograph is his son.
Hence, the answer is (b).