Series test fillup of alphabets

Find the next triplet of alphabets in the following series. ABD, DGK, HMS, MTB, SBL, ?

If the alphabets are numbers the sum of which 5 alphabets is 51

What will be the next set of alphabets in the series ? CW, DU, ES, ?

The following groups of alphabets from a certain pattern with regard to their position in the English alphabetic series. Based upon the pattern which of the following five alternative shall replace the question mark? AD FC HK MJ ?

The following groups of alphabets from a certain pattern with regard to their position in the English alphabetic series. Based upon the pattern which of the following five alternative shall replace the question mark? XDH VGJ TJL RMN ?

In each of the following questions, a series of number / alphabet is given which follow certain rules. One of the number / alphabet is missing. Choose the missing number / alphabets from the alternatives given below and mark it on your answer - sheet as directed. 18, 24, 21, 27, ?, 30, 27,

In each of the following questions, a series of number / alphabet is given which follow certain rules. One of the number / alphabet is missing. Choose the missing number / alphabets from the alternatives given below and mark it on your answer - sheet as directed. ELFA, GLHA, ILJA, ? , MLNA

In the following question, a series is given with one alphabet missing. Choose the correct alternative from the given options. L, C, M, B, N, A, O ?