Three of the following letter-clusters are alike in some manner and hence form a group. Which letter-cluster does not belong to that group?

Correct option is B

1) FKA => F + 5 = K, F – 5 = A
2) CJZ => C + 5 = H, J – 10 = Z
3) PUK => P + 5 = U, P – 5 = K
4) CHX => C + 5 = H, C – 5 = X
Option (2) is odd one because except this all others are follow same pattern.