Which of the following letter-clusters will replace the question mark (?) in the given series to make it logically complete?

TJV, WFY, ZBB, CXE, ?​​

​TJV, WFY, ZBB, CXE, ?​​

1st letters: T + 3 = W, W + 3 = Z, Z + 3 = C, C + 3 = F

2nd letters: J − 4 = F, F − 4 = B, B − 4 = X, X − 4 = T

3rd letters: V + 3 = Y, Y + 3 = B, B + 3 = E, E + 3 = H

 FTH will be next term.

Thus, correct option is (a).