Which of the following letter-clusters will replace the question mark (?) in the given series? WNM, ULO, SJQ, QHS

Which of the following letter-clusters will replace the question mark (?) in the given series? WNM, ULO, SJQ, QHS, ?

A.            OFU

B.            PFS

C.            OGU

D.            PGT

Sol:

Pattern follows here is: -2, -2, +2

The required term is: OFU.