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 + 1 = 3rd letter and 2nd letter + 1 = 4th letter
Now, we check each options.
​Option (a): ​PN-QO (Follow)

P + 1 = Q, N + 1 = O
​Option (b): QO-RP (Follow)​

Q + 1 = R, O + 1 = P
​Option (c): LJ-MK (Follow)​

L + 1 = M, J + 1 = K 
​Option (d): ​US-UV​ (Not Follow)​

U + 1 $$\neq$$​ U, S + 1 $$\neq$$​ V
Thus, correct option is (d).