Four options have been given, out of which three are alike in some manner and one is different. Select the odd one.

Option A: BFWT
B (2) ↔ W (23) (Not an exact opposite pair)
F (6) ↔ T (20) (Not an exact opposite pair)
Does NOT follow the alternate opposite letter pattern
Option B: EHVS
E (5) ↔ V (22) 
H (8) ↔ S (19) 
Follows the alternate opposite letter pattern
Option C: MONL
M (13) ↔ N (14) 
O (15) ↔ L (12)  
​Follows the alternate opposite letter pattern

Option D: ACZX
A (1) ↔ Z (26) 
C (3) ↔ X (24) 
Follows the alternate opposite letter pattern
Odd One Out:

Each option (except BFWT) follows the pattern where letters are placed in alternate opposite positions in the alphabet.

Therefore, BFWT is the odd one out because it does not follow the alternate opposite pattern.

Thus, the correct option is (a)