Based on the English alphabetical order, three of the following four letter - clusters are alike in a certain way and thus form a group. Which letter - cluster 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 letter + 2 = 2nd letter and 2nd letter + 3 = 3rd letter

Now, we check each options.

Option (a): GIL (Follow)

G + 2 = I, I + 3 = L

Option (b): SUW (Not Follow)​

S + 2 = U, U + 3 $$\neq$$​ W

Option (c): KMP (Follow)​

K + 2 = M, M + 3 = P

Option (d): EGJ (Follow)​

E + 2 = G, G + 3 = J

Thus, correct option is (b).