Find odd one out?

The correct option is PLR.

To find the odd one out, let us analyze the positional values of the letters in the English alphabet for each option:

1. FBI:
F = 6
B = 2
I = 9
Notice that the position of the third letter is the sum of the positions of the first two letters:
6 + 2 = 8 (Wait, let's check another pattern or relationship).

Let me re-examine the positions of the letters in each triplet:
FBI: F(6), B(2), I(9) → 6 + 2 + 1 = 9 or (6 - 2 = 4, etc.)
EAH: E(5), A(1), H(8) → 5 + 1 + 2 = 8?
Let me look closely at the positions:
FBI: F = 6, B = 2, I = 9. Sum = 6 + 2 + 9 = 17.
PLR: P = 16, L = 12, R = 18. Sum = 16 + 12 + 18 = 46.
EAH: E = 5, A = 1, H = 8. Sum = 5 + 1 + 8 = 14.
IEL: I = 9, E = 5, L = 12. Sum = 9 + 5 + 12 = 26.
RNU: R = 18, N = 14, U = 21. Sum = 18 + 14 + 21 = 53.

Let's check the difference between consecutive letters or another logical rule:
- FBI: F (6) → B (2) [-4], B (2) → I (9) [+7]
- EAH: E (5) → A (1) [-4], A (1) → H (8) [+7]
- IEL: I (9) → E (5) [-4], E (5) → L (12) [+7]
- RNU: R (18) → N (14) [-4], N (14) → U (21) [+7]
- PLR: P (16) → L (12) [-4], L (12) → R (18) [+6]

As seen from the pattern:
In FBI, EAH, IEL, and RNU, the first letter moves backwards by 4 positions (-4) to get the second letter, and the second letter moves forward by 7 positions (+7) to get the third letter.

However, in PLR, P (16) to L (12) is -4, but L (12) to R (18) is +6 instead of +7.

Therefore, PLR is the odd one out.