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 is the letter cluster pair that DOES NOT belong to that group?
(Note: The odd man out is not based on the number of consonants/vowels or their position in the letter cluster.)

Let's check the options:

First option: DGIL; D + 3 = G, G + 2 = I, I + 3 = L

Second option: CEHK; C + 2 = E, E + 3 = H, H + 3 = K

Third option: BEGJ; B + 3 = E, E + 2 = G, G + 3 = J

Fourth option: ADFI; A + 3 = D, D + 2  = F, F + 3 = I

So, only the letters in the second option follow a different pattern.

Thus, the correct answer is (b).