Data sufficiency – tallest among six boys Who is the tallest among P, T, N, D, Q, and R? Statements: (I) P is taller than D and N but not as tall as T. (II) R is taller than Q but not as tall as T. (III) Q is not taller than T and R.

Introduction / Context:
The task is to determine the tallest person using comparative height statements. We only need to know which set of statements is sufficient, not to fully order everyone.

Given Data / Assumptions:

• Statement I: T taller than P; P taller than D and N.
• Statement II: T taller than R; R taller than Q.
• Statement III: Q is not taller than T and R (i.e., Q shorter than both).

Concept / Approach:
Combine inequalities to check if anyone could be taller than T. If no statement asserts anyone taller than T, and T is shown taller than all others, T is tallest and the set is sufficient.

Step-by-Step Solution:

Verification / Alternative check:
Try to construct a counterexample where someone exceeds T under I + II: impossible because each other person is directly shown lower than T. Hence I + II are sufficient.

Why Other Options Are Wrong:

• Only II and III / Only I and III: Leave open the possibility that P (or R) could be taller than T.
• All I, II and III: Sufficient but not minimal; data sufficiency asks for the minimal correct option set.
• Only I and either II or III: I + III alone is not sufficient.

Common Pitfalls:
Assuming transitivity without checking all individuals, or treating 'not taller than' as 'shorter than or equal to' and overlooking that equality would not change the conclusion since only strict 'taller than' statements fix T above key rivals.

Final Answer:
Only I and II