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

ROM : SRT :: PNA : ?

QQH

Pattern followed is :

ROM : SRT

R(18) + 1 = (19)S , O(15) + 3 = (18) , M(13) + 7 = (20)T

Similarly ,

PNA : ?

P(16) +  1 = (17)Q , N(14) + 3 = (17)Q , A(1) + 7 = (8)H

QQH is correct answer .