A and B are children of D. Who is the father of A ? To answer this question which of the statements $\left(1\right)$ and $\left(2\right)$ is necessary ?
1. C is the brother of A and the son of E.
2. F is the mother B.

The correct option is B Only $\left(2\right)$
A and B are children of D.
From $\left(1\right)$, C is the brother B and son of E.
Since, the sex of D and E are not known. Hence $\left(1\right)$ is not sufficient to answer the question.
From $\left(2\right)$. F is the mother of B. Hence, F is also the mother of A. Hence D is the father of A.
Thus, $\left(2\right)$ is sufficient to answer the question.

option B.