Choose the odd pair: In these pairs A–B, most have a constant difference of −3 (B = A − 3). Identify the pair that does not follow this pattern.

Introduction / Context:
Constant-difference relations are common in classification items. Here, the expected relation is B = A − 3, i.e., the second number is 3 less than the first. Find the pair that breaks this consistency.

Given Data / Assumptions:

• Pairs: 5–2, 19–16, 27–23, 31–28.
• We measure B − A to confirm the difference.

Concept / Approach:
Compute A − B (or B − A) and check whether the difference equals 3 consistently. The odd pair will have a different gap.

Step-by-Step Solution:

Verification / Alternative check:
Using B − A gives −3, −3, −4, −3 respectively. The lone −4 confirms 27–23 as the violator.

Why Other Options Are Wrong:
They fit the −3 pattern exactly and therefore are not the odd item.

Common Pitfalls:
Miscalculating simple differences, especially when scanning quickly. A one-off mistake can hide the true odd pair.

Final Answer:
27 - 23 is the odd pair.