Choose the missing terms out of the given alternatives : ABD , DGK, HMS, MTB, SBL, ?

Answer: Option D

1st letter : A + 3 = D + 4 = H + 5 = M + 6 = S + 7 = Z
2nd letter : B + 5 = G + 6 = M + 7 = T + 8 = B + 9 = K
3rd letter : D + 7 = K + 8 = S + 9 = B + 10 = L + 11 = W