Correct Option
Statements S1 and S3 together are sufficient to answer the question.
- Statement S1 provides the relationships: C is younger than D (D > C), and C is older than both A and B (C > A and C > B).
- Statement S3 provides the relationship: A is older than B (A > B).
- By combining these two statements:
- From S1, we establish D > C.
- Also from S1, C is older than A and B.
- From S3, we know A is older than B.
- Integrating these relationships sequentially leads to the complete age order: D > C > A > B.
- Based on this combined order, B is unequivocally identified as the youngest among A, B, C, and D.
Incorrect Options:
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Option 1 (S1 alone is sufficient): Statement S1 (D > C > A and D > C > B) indicates that C is older than both A and B. However, it does not specify the age relationship between A and B. Consequently, the youngest person could be either A or B, making S1 alone insufficient to determine the youngest.
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Option 2 (S1 and S2 together are sufficient): Statement S1 provides D > C > A and D > C > B. Statement S2 states that D is the oldest. This information from S2 is partially redundant with S1 (D > C) and does not resolve the ambiguity regarding the relative ages of A and B. Therefore, the youngest remains uncertain between A and B, making S1 and S2 together insufficient.
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Option 3 (S2 and S3 together are sufficient): Statement S2 establishes D as the oldest. Statement S3 establishes A > B. Combining these yields D > A > B. However, the position of C relative to A and B is not defined. C could be older than A, younger than A but older than B, or younger than B. Thus, the youngest could be either B or C, rendering S2 and S3 together insufficient.