Which of the following letter-number clusters will replace the question mark (?) in the given series to make it logically complete?
ADB 1, EHF 4, ILJ 16, MPN 64, ?

Given: ​ADB 1, EHF 4, ILJ 16, MPN 64, ?

Logic: Letters are increasing + 4 and number is multiply by 4 each time.

For, letters

A + 4 = E, E + 4 = I, I + 4 = M, M + 4 = Q

D + 4 = H, H + 4 = L, L + 4 = P, P + 4 = T

B + 4 = F, F + 4 = J, J + 4 = N, N + 4 = R

For, number 

1 $$\times$$ 4 = 4, 4 $$\times$$ 4 = 16, 16 $$\times$$ 4 = 64, 64 $$\times$$ 4 = 256​

So, the missing term is QTR 256.

Thus, correct option is (d).