Data Sufficiency — Linear Seating (Who Sits in the Middle?) Among P, Q, R, S, and T in a straight line facing North, who sits exactly in the middle? I. P sits third to the left of S. T is an immediate neighbour of both P and R. II. T sits second to the left of S. Q is not an immediate neighbour of T or S.

Introduction / Context:
We must identify the exact middle seat using two incomplete linear constraints.

Given Data / Assumptions:

• I gives a 3-left relation between P and S and binds T to both P and R, leaving multiple valid permutations.
• II fixes T two-left of S and restricts Q’s adjacency, but still allows multiple permutations.

Concept / Approach:
Each statement alone permits more than one arrangement; combining them typically collapses to a unique layout, hence a unique middle person.

Step-by-Step Solution:

Verification / Alternative check:
Quick backtracking shows single consistent ordering when both are enforced.

Why Other Options Are Wrong:
I alone or II alone: multiple possibilities; either alone false; “even both not sufficient” is false.

Common Pitfalls:
Forgetting everyone faces North (left/right are absolute), or placing two people in one seat.

Final Answer:
Both statements together are sufficient; neither alone is sufficient.