Based on the English alphabetical order, three of the following four letter-cluster thus form a group. Which 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 B

Option a ,  VS-PU

V - 6 = P

S + 2 = U

Option b, YV-SW

Y - 6 = S

V + 2 = X  not W

Option c - RO-LQ

R - 6 = L

O + 2 = Q    

Option d, TQ-NS

T - 6= N

Q + 2 = S

All follows the same logic except option b . so option b is odd one out.