A and B are children of D. Who is the father of A? To answer this question…
2024
A and B are children of D. Who is the father of A? To answer this question which of the statements (1) and (2) is necessary?
C is the brother of A and the son of E.
F is the mother of B.
- A.
Only (1)
- B.
Only (2)
- C.
Either (1) or (2)
- D.
(1) and (2) both
Show answer & explanation
Correct answer: B
In a Data Sufficiency question, a statement is 'sufficient' only if it lets you arrive at one single, definite answer to the question asked. Each statement must first be tested completely on its own; the two statements are combined only if neither one works alone.
From the question: A and B are children of D, and the father of A has to be identified.
Statement (1): C is the brother of A and the son of E. This only places C as a sibling of A and a child of E; it never fixes the gender of D or E, so it cannot tell us who is male and who is female among the parents. Statement (1) alone is NOT sufficient.
Statement (2): F is the mother of B. From the question stem, D is already known to be a parent of B. Since a person can have only one mother, D — being the other named parent of B — must be male, i.e. the father of B. D is the very same person who is also stated to be a parent of A, so D's gender does not change between the two children; hence D is the father of A as well. Statement (2) alone IS sufficient.
Since statement (2) alone answers the question and statement (1) contributes nothing extra to it, the correct choice is the one stating that only statement (2) is necessary.