Choose the correct option: Find the odd man out.

Concept: In this family of three-letter codes, each triple is built by applying a fixed shift twice: the middle letter is the first letter moved forward by 1 position in the alphabet, and the last letter is the middle letter moved forward by 2 positions, wrapping from Z back to A when a shift crosses the end of the alphabet. A triple that does not satisfy both shifts is the odd one out.

Applying this rule to each code:

• STV: S moves 1 step to T (matches), and T moves 2 steps to V (matches) — the shift holds throughout.

• XYA: X moves 1 step to Y (matches), and Y moves 2 steps forward, wrapping past Z to A (matches) — the shift holds with wrap-around.

• BCE: B moves 1 step to C (matches), and C moves 2 steps to E (matches) — the shift holds throughout.

• KKT: K should move 1 step to L, but the middle letter stays K instead — the +1 shift fails right here, before the third letter is even reached.

Cross-check: Numbering the letters A=1...Z=26, K = 11, so the expected second letter is K+1 = 12 = L. The given second letter is K (11), i.e. no shift at all — confirming the break happens right there, independent of the third letter.

Result: KKT does not follow the +1 then +2 shift that the other three codes share, so it is the odd man out.