Find the odd 4-letter block (−3, −1, +3 signature): Pick the option that does not follow the pattern “−3, −1, +3”.

Introduction / Context:
Four-letter sequences can encode a three-step signature in terms of alphabet index differences. When most items share a fixed signature, the single deviation is the odd one out.

Given Data / Assumptions:

• GDCF: G→D (−3), D→C (−1), C→F (+3) → fits.
• LIHK: L→I (−3), I→H (−1), H→K (+3) → fits.
• TQPS: T→Q (−3), Q→P (−1), P→S (+3) → fits.
• RNMQ: R→N (−4), N→M (−1), M→Q (+4) → does not fit (−4, −1, +4).

Concept / Approach:
Convert letters to indices and compute successive differences. The outlier will violate the consistent “−3, −1, +3” pattern used by the others.

Step-by-Step Solution:

Verification / Alternative check:
Reverse-direction checks preserve the mismatch, confirming RNMQ as the deviation.

Why Other Options Are Wrong:
They conform exactly to the intended signature.

Common Pitfalls:
Do not mix up sign and magnitude; both must match the signature.

Final Answer:
RNMQ