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.)

Correct option is C

Let's check the options:
Logic: 1st letter − 3, 2nd letter + 5 (alphabet positions). 

Option (A) IL → FQ:
I − 3 = F , L + 5 = Q 
Option (B) WR  → TW:
W − 3 = T , R + 5 = W 
Option (C) HY  → DD:
 H − 3 = E ≠ D , Y + 5 = D →Odd one out
Option (D) QE → NJ:
 Q − 3 = N, E + 5 = J 
Thus, the correct answer is (C) HY → DD.