In each of the following letter series, some of the letters are missing which are given in that order as one of the alternatives below it. Choose the correct alternative.

ab _ aa _ bbb _ aaa _ bbba

Answer: Option B

Explanation:

The series is abb/aaabbb/aaaabbbb/a. Thus the letters are repeated twice, then thrice, then four times and so on.

_ nmmn _ mmnn _ mnnm _

Answer: Option C

The series is nnmm/nnmn/nnmm/nnmm. Thus, the pattern 'nnmm' is repeated.

a _ n _ b _ _ ncb _ _ ncb

Answer: Option D

The series is abncb/abncb/abncb. Thus, the pattern 'abncb' is repeated.

a _ ba _ b _ b _ a _ b

The series is abb/abb/abb/abb. Thus, the pattern 'abb' is repeated.

cccbb _ aa _ cc _ bbbaa _ c

The series is ccc bbb aaa/ccc bbb aaa/c. Thus, the pattern ccc bbb aaa is repeated.