Explanation

To determine the odd pair, we look at the alphabetical order and the pattern between the letters:

CE: C (3rd letter), E (5th letter) – Difference is 2

FH: F (6th letter), H (8th letter) – Difference is 2

IK: I (9th letter), K (11th letter) – Difference is 2

LM: L (12th letter), M (13th letter) – Difference is 1

The pairs CE, FH, and IK have a consistent pattern where the difference between the positions of the letters is 2.

However, in LM, the difference is 1, making it the odd one out.