Ответ:

  1. F — the other letters are in alphabetical order: A, B, C.
  2. Q — the other letters are in alphabetical order: M, N, O.
  3. Y — the other letters are in alphabetical order: S, T, U.
  4. K — the other letters are in alphabetical order: G, H, I.
  5. F — the other letters are in alphabetical order: P, Q, R.

Answers: 1) F; 2) Q; 3) Y; 4) K; 5) F.