alphanumeric series completion Model Questions & Answers, Practice Test for ibps clerk mains

Which one of the following is the correct order of missing letters in the series given below ?
aab _ aa _ bbb _ aaa _ bbba

Which one of the following is the correct order of missing letters in the series given below ?
a _ n _ b _ _ ncb _ _ ncb

Which one of the following is the correct order of missing letters in the series given below ?
ac _ cab _ baca _ aba _ acac

Which of the following will come in place of the question mark(?) in the order given below?
A B A B C B C B C D C D?

The following groups of alphabets form a certain pattern with regard to their position in the English alphabetical series. Based upon the pattern, which of the following five alternatives should replace the question mark?
XDH, VGJ, TJL, RMN, ?