Pointing a photograph X said to his friend Y, “She is the only daughter of the father of my mother.” How X is related to the person of photograph?

The correct answer is C. Nephew.

The person in the photograph is the only daughter of the father of X’s mother. This means that she is X’s aunt. X’s aunt’s child is X’s nephew.

Option A is incorrect because X is not the daughter of the person in the photograph.

Option B is incorrect because X is not the son of the person in the photograph.

Option D is incorrect because it is possible to determine how X is related to the person in the photograph.