Explanation:

Let’s break down the options:

- CX: C is the 3rd letter, X is the 24th. The forward difference is 21.

- HS: H is 8, S is 19. The difference: 11.

- BY: B is 2, Y is 25. The difference: 23.

- JP: J is 10, P is 16. The difference: 6.

Now, look closer. For options CX, HS, and BY, the two letters are always the 3rd from start and 3rd from end (C-X, H-S, B-Y). But JP? J isn’t the 10th from start, or P the 10th from end; the positions aren’t mirrored. JP breaks the pattern.

Option: 4 - JP is the odd pair out.