"How is P related to Q" ?
1) Q is the father of P.
2) S is the brother of P.

Options

A. Son
B. Daughter
C. Sister
D. either 1 or 2

Explanation

We see that statement (1) says that Q is the father of P. Is it enough to conclude how P is related to Q? No. P could be a son or may as well be a daughter of Q. Hence, to establish exactly how P is related to Q, we must also know the sex of P, i.e., whether P is a male or a female. This information can be given directly in the wording "P is a male/female" or indirectly in the wording (such as):
a. P is a brother/sister of (say) X.
b. P is the father/mother of (say) X.
c. P is an uncle/aunt of (say) X.