Three of the following four letter-clusters are alike in a certain way and one is different. Pick the odd one out

Three of the following four letter-clusters are alike in a certain way and one is different. Pick the odd one out.

A.            XCY

B.            OLP

C.            TGU

D.            BXC

Sol:

Except option D, the pattern follows here is (a, b, c)

B = Opposite alphabet of A, C = A+1.