Complete each 4-letter block so all four become P Q R S with one different letter missing in each. Blocks: P Q R _, P Q _ S, P _ R S, _ Q R S

Introduction / Context:
Each block is the set {P, Q, R, S} with one omission. Across the four blocks, the missing letters should cover S, R, Q, P exactly once.

Given Data / Assumptions:
Blocks: PQR_, PQ_S, P_RS, _QRS.

Concept / Approach:
Identify the missing letter per block in order, then read those four letters to form the answer choice.

Step-by-Step Solution:

Verification / Alternative check:
Insert S, R, Q, P respectively and each block becomes PQRS.

Why Other Options Are Wrong:
They present a different order of missing letters than the one dictated by the underscores.

Common Pitfalls:
Misreading positions of the underscores.

Final Answer:
SRQP