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.

_ aa _ ba _ bb _ ab _ aab

Answer: Option C

Explanation:

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

c _ bba _ cab _ ac _ ab _ ac

Answer: Option B

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

ba _ cb _ b _ bab _

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

_ bc _ ca _ aba _ c _ ca

Answer: Option A

The series is abc/bca/cab/abc/bca, Thus, the letters change places in a cyclic order.

ab _ _ baa _ _ ab _

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