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

CAST : DCVX :: BUSH : CWVL :: ARMY : ?

BTPC

Pattern followed here is :

CAST : DCVX                                  &               BUSH : CWVL

C(3)+1 = (4)D                                            B(2)+1 = (3)C

A(1) + 2 = (3)C                                          U(21)+2=(23)W

S(19)+3 = (22)V                                         S(19)+3 =(22)V

T(20)+4 = (24)X                                         H(8)+4 = (12)L

Similarly ,

ARMY : ?

A(1)+1 = (2)B

R(18)+2=(20)T

M(13)+3 = (16)P

Y(25)+4 = (3)C

Hence BTPC is correct answer .