P and Q are brothers. P is the father of S. R is the only son of Q and is married to U. Based on these relations, how is U related to S?

Introduction / Context:
This blood relation question involves two brothers P and Q, their children S and R, and R's wife U. We are asked to determine how U is related to S. The problem highlights the relation between cousins and the spouses of cousins, which in many reasoning questions are treated as brothers in law or sisters in law.

Given Data / Assumptions:
• P and Q are brothers.• P is the father of S.• R is the only son of Q.• R is married to U.• Standard family terms are used without any special meaning.

Concept / Approach:
Since P and Q are brothers, their children are cousins. That means S, child of P, and R, child of Q, are first cousins. U is the wife of R. In many family relation questions and in ordinary language, the spouse of a cousin is referred to as a brother in law or sister in law. From S's perspective, U is the wife of her male cousin R. Hence U is S's sister in law. The question is simply checking recognition of this extended in law relation.

Step-by-Step Solution:
Step 1: P and Q are brothers, so they are in the same generation and share parents.Step 2: S is the child of P, so S belongs to the next generation.Step 3: R is the only son of Q, so R is also in the next generation.Step 4: Because their fathers P and Q are brothers, S and R are cousins.Step 5: R is married to U, making U the spouse of S's cousin.Step 6: The spouse of a cousin is generally treated as brother in law or sister in law.Step 7: Since U is female, she is the sister in law of S.

Verification / Alternative check:
Picture a family where two brothers P and Q each have one child. The child of P is S, and the child of Q is R. When R marries U, U becomes part of the extended family. The tie between S and U comes entirely through R. This is neither a direct sibling nor a parent child relation. In many standard exam explanations, the correct label for this relation is sister in law, which is the matching option provided.

Why Other Options Are Wrong:
Mother in law of S: For this, U would need to be the mother of S's spouse, which is not given.Sister of S: Sisters share the same parents, which is not the case here.Mother of S: P is explicit parent of S; U is not in the parental generation.Cousin of S: R is the cousin; U is an in law connected through R.

Common Pitfalls:
Candidates sometimes think only siblings of a spouse can be brothers in law or sisters in law and forget that in many exam questions the spouse of a cousin is also treated as a sister in law. It is crucial to read the question in the context of commonly used relations in reasoning problems, where cousin's spouse often falls under the in law category.

Final Answer:
U is the sister in law of S.