Select the letter-cluster that can replace the question mark (?) in the following series.

MOM, QSQ, UWU, ?

Given: MOM, QSQ, UWU, ?

Logic: Letters are increasing + 4 in English alphabetical order.

1st letter: M + 4 = Q, Q + 4 = U, U + 4 = Y

2nd letter: O + 4 = S, S + 4 = W, W + 4 = A

3rd letter: M + 4 = Q, Q + 4 = U, U + 4 = Y

So, the next series is YAY.

Thus, correct option is (b).