A series of letter pairs is given with one pair missing. Select the pair that continues the pattern: HI, MN, RS, ?

Introduction / Context:
This is a simple alphabetic pair sequence where each pair consists of two consecutive letters. The starting letters progress forward through the alphabet. Your task is to identify the next pair that keeps this development consistent.

Given Data / Assumptions:

• Given pairs: HI, MN, RS, ? • Alphabet positions: A = 1 to Z = 26. • Each pair is composed of consecutive letters (H with I, M with N, etc.). • The first letters follow a regular forward step pattern.

Concept / Approach:
We focus on the first letters: H, M, and R. Converting them into numbers reveals a constant step size. Once we know how the first letters move, we automatically know the second letters because each pair is consecutive. This is a classic pattern used to test familiarity with letter positions and simple addition.

Step-by-Step Solution:
Step 1: Translate first letters to numeric positions. H = 8, M = 13, R = 18. Differences: 8 → 13 is +5, 13 → 18 is +5. So we add 5 each time. Next first letter: 18 + 5 = 23, which is W. Step 2: Determine the second letter of the pair. Each pair uses consecutive letters, so after W the next letter is X. Thus, the missing pair is WX.

Verification / Alternative check:
Sequence of first letters: H, M, R, W corresponds to 8, 13, 18, 23. The differences are consistently +5. Second letters automatically follow as I, N, S, X (9, 14, 19, 24). This yields the smooth series HI, MN, RS, WX. No other option gives a pair whose first letter is exactly five positions after R.

Why Other Options Are Wrong:
• XY: X is six positions after R, not five, so this breaks the constant step pattern. • WY: W is correct as a first letter, but Y is not consecutive with W and thus fails the internal structure of pairs. • WE: E is far earlier in the alphabet than expected and does not follow from W as a consecutive second letter.

Common Pitfalls:
Some candidates notice only that the first letters are spaced out and guess based on rough distances instead of computing exact differences. Others forget that the letters of each pair themselves must be consecutive. Carefully checking both the step size for first letters and the internal relation within pairs avoids such errors.

Final Answer:
The pair that correctly completes the pattern is WX.