Choose the odd one out.

Concept

Concept: In an alphabet-series classification set, three (or more) of the given letter-groups are built by applying the SAME fixed sequence of forward/backward alphabet-position jumps to generate each next letter from the first letter of the group. The one group that does not follow this shared step-pattern is the odd one out.

Application

Application - deriving the shared pattern:

1. In ADCB: A (position 1) moves forward 3 positions to D (position 4); D moves back 1 position to C (position 3); C moves back 1 position to B (position 2). Step pattern: +3, -1, -1.

2. In NQPO: N (position 14) moves forward 3 positions to Q (position 17); Q moves back 1 position to P (position 16); P moves back 1 position to O (position 15). Step pattern: +3, -1, -1 - the same pattern as ADCB.

3. In WZYX: W (position 23) moves forward 3 positions to Z (position 26); Z moves back 1 position to Y (position 25); Y moves back 1 position to X (position 24). Step pattern: +3, -1, -1 - again the same pattern.

4. In GJHI: G (position 7) moves forward 3 positions to J (position 10), matching the first step; but J then moves back 2 positions to H (position 8), not 1; and H then moves forward 1 position to I (position 9), not back 1. Step pattern: +3, -2, +1 - this breaks the shared +3, -1, -1 pattern.

Cross-check

Cross-check: Three of the four groups (ADCB, NQPO, WZYX) share the exact +3, -1, -1 step-pattern regardless of the starting letter, confirming the pattern is genuine and not coincidental. GJHI is the only group whose steps deviate from it.

Hence, GJHI is the odd one out.