Based on the English alphabetical order, three of the following four letter-cluster pairs are alike in a certain way and thus form a group. Which letter-cluster pair DOES NOT belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)​

Logic: 1st - 5 = 3rd, 2nd - 5 = 4th 

a) BZ − WU
B - 5  = W
Z - 5 = U
b). YW − TR
Y - 5 = T
W - 5 = R
c). MK − GH
M - 6 = G
K - 3 = H (Not follow)
d). KI − FD
K - 5 = F
I - 5 = D
Thus, the correct option is (c).