Find the missing letters in the following series.
UJ, SM, QQ, OV, ?

Given: UJ, SM, QQ, OV, ?

The first letters of each term: U, S, Q, O

U - 2 = S, S - 2 = Q. Q - 2 = O

The second letters of each term: J, M, Q, V

J + 3 = M, M + 4 = Q, Q + 5 = V

Same logic is apply on next term,

O - 2 = M,

V + 6 = B

So, MB is next term.

Thus, the correct answer is (a).