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 letter - 7 = 3rd letter and 2nd lette + 7 = 4th letter

Now, we check each options.

Option (a): KP – DW (Follow)

K - 7 = D, P + 7 = W

Option (b): RW – LD (Not Follow)​

R - 7 $$\neq$$​ L, W + 7 = D

Option (c): UZ – NG (Follow)​

U - 7 = N, Z + 7 = G

Option (d): CH – VO (Follow)​

C - 7 = V, H + 7 = O

Thus, correct option is (b).