1.  Questions : How many sons does X have ?
statements : 

I.   Q and U are brothers of T.
II.  R is sister of P and U.
III. R and T are daughters of X.

A. Only I and II
B. Only II and III
C. All I, II and III
D. I, II and III together are not sufficient.
E. None of these

Answer: Option D

Explanation:

From I, II and III, we conclude that all P, Q, T, and U are children of X.Of these, to Q and U are male while R and T are female. But the sex of P cannot be determined.