A is the father of X. B is the mother of Y. The sister of X and Z is Y (i.e., Y is the sister of both X and Z). Which statement is definitely true?

Question

Solve this multiple-choice question and choose the correct option.

Accepted Answer

Introduction / Context:“Definitely true” questions test whether you can distinguish what is guaranteed from what is merely possible. The statements intentionally leave some parental links unspecified. You must not assume missing links (like both parents being the same) unless stated. We will analyze each option under all legal configurations and select the one that holds in every case. Given Data / Assumptions: A is father of X (A → father → X). B is mother of Y (B → mother → Y). Y is the sister of both X and Z (so Y is female and is a sibling of X and Z). Nothing explicitly states that X and Y share both parents, only that they are siblings (sharing at least one parent). Concept / Approach:Mark certainties: Y is female (called “sister”), and B is the mother of Y. Hence B has at least one daughter: Y. That is a universal truth across all scenarios. Other options require assumptions about who the common parent(s) are for X, Y, Z, which the stem does not fix. Step-by-Step Solution: Option (a) “B is the mother of Z.” Not guaranteed. Y is Z’s sister, but siblings can share only one parent; Z could share the father side, not necessarily B as mother.Option (b) “X is the sister of Z.” X’s gender is unknown; X could be male. Not definitely true.Option (c) “Y is the son of A.” Contradicts “Y is the sister …,” which marks Y as female. Definitely false.Option (d) “B has one daughter.” Guaranteed minimal truth: B is mother of Y, and Y is explicitly female. Even if B has additional daughters, the statement “has one daughter” can be read as “has at least one daughter” in many test conventions. Interpreted strictly as “exactly one,” it would be unsafe; however, standard verbal-reasoning keys intend the definite takeaway that B is confirmed to be the mother of a daughter (Y). Among the given options, this is the only universally valid inference.Option (e) “None of these.” Not correct because (d) captures the definite fact implied by the stem. Verification / Alternative check:Construct edge cases: If X and Y share father A but different mothers, B remains the mother of Y alone—still B has a daughter. If all three share both parents A and B, B still has a daughter. Hence (d) persists universally. Why Other Options Are Wrong: (a) Depends on whether Z's mother is B; not specified. (b) Requires X to be female; not stated. (c) Conflicts with Y being female. Common Pitfalls: Assuming all siblings share both parents when the problem never states this. Ignoring explicit gender markers like “sister.” Final Answer: B has one daughter

A is the father of X. B is the mother of Y. The sister of X and Z is Y (i.e., Y is the sister of both X and Z). Which statement is definitely true?

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