Select the option that is related to the fifth alphanumeric-cluster in the same way as the second alphanumeric-cluster is related to the first alphanumeric-cluster and the fourth alphanumeric-cluster is related to the third alphanumeric-cluster.

MNO13 : QRS17 :: PQR16 : TUV20 :: STU19 : ?

WXY23

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

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

MNO13 : QRS17 :: PQR16 : TUV20 :: STU19 : ?

The  logic followed here is :

M → (+4) → Q

N → (+4) → R

O → (+4) → S

13 → (+4) → 17

AND

P → (+4) → T

Q → (+4) → U

R → (+4) → V

16 → (+4) → 20

SIMILARLY

S → (+4) → W

T → (+4) → X

U → (+4) → Y

19 → (+4) → 23