Classification – Odd one out (letter-step pattern): Choose the string that breaks the −2, −3, −4 backward-step pattern: MKHD, JHEA, QNKH, XVSO.

Introduction / Context:
Many alphabet puzzles encode a fixed sequence of backward jumps (e.g., −2, −3, −4) across four letters. The majority of options adhere to a specific jump signature, while one deviates. We confirm by converting letters to positions A=1, B=2, …, Z=26.

Given Data / Assumptions:

• Strings: MKHD, JHEA, QNKH, XVSO.
• Backward step sizes are measured as position differences.

Concept / Approach:
Compute consecutive steps for each string. A consistent signature (−2, −3, −4) across three items will identify the rule. The string that fails that signature is the outlier.

Step-by-Step Solution:
MKHD: M(13)→K(11) = −2; K(11)→H(8) = −3; H(8)→D(4) = −4.JHEA: J(10)→H(8) = −2; H(8)→E(5) = −3; E(5)→A(1) = −4.XVSO: X(24)→V(22) = −2; V(22)→S(19) = −3; S(19)→O(15) = −4.QNKH: Q(17)→N(14) = −3; N(14)→K(11) = −3; K(11)→H(8) = −3 (not −2, −3, −4).

Verification / Alternative check:
Try reading right to left; the three compliant strings then become +4, +3, +2, but QNKH still has equal steps. In both directions, QNKH violates the expected graduated differences.

Why Other Options Are Wrong:

• MKHD, JHEA, XVSO: all strictly follow −2, −3, −4.

Common Pitfalls:
Looking only for monotonicity and missing the graded step sizes. The rule is not just decreasing; it is decreasing by 2, then 3, then 4.

Final Answer:
QNKH