Data sufficiency — Who is the uncle of L? Statements: A. P, brother of M, is father of L; M is father of S. B. R is father of L's cousin. Decide which statements are sufficient to determine the uncle of L.

Introduction / Context:
The task is to identify L’s uncle using data sufficiency. We must determine whether each statement alone (or together) pins down a unique answer.

Given Data / Assumptions:

• A: P and M are brothers; P is father of L; M is father of S.
• B: R is father of L’s cousin (ambiguous without further ties).

Concept / Approach:
An uncle is a brother of a parent (or spouse thereof, depending on convention). From A, we know P is L’s father and that P’s brother is M, i.e., M is paternal uncle of L.

Step-by-Step Solution:

Verification / Alternative check:
Under A, there is no ambiguity: the uncle is M. Under B, R could be any cousin’s father through various family branches; multiple possibilities exist.

Why Other Options Are Wrong:

• B alone: Too vague to identify a unique uncle.
• Either A or B: False, as B fails.
• Both not sufficient: False, A is already sufficient.
• A and B together: Redundant since A alone suffices.

Common Pitfalls:
Mistaking any cousin’s parent as automatically an uncle; overlooking that “cousin” may arise from either parent’s siblings.

Final Answer:
A alone is sufficient.