Select the option that is related to the third letter-cluster in the same way as the second letter-cluster is related to the third letter cluster.

RJB : TGF :: QPG : ?

SMK

A   B   C    D   E    F   G    H    I    J    K    L   M

 ↓    ↓    ↓    ↓    ↓     ↓   ↓    ↓     ↓   ↓    ↓    ↓    ↓

 Z   Y    X   W   V    U   T    S    R   Q   P    O   N

26  25  24  23  22  21  20  19  18  17  16  15  14

******************************************

RJB : TGF :: QPG : ?

The  logic followed here is :

R → (+2)→ T

J → (-3)→ G

B → (+4)→ F

SIMILARLY

Q → (+2)→ S

P → (-3)→ M

G → (+4)→ K