Correct Answer: c b c a a

Solution : Given:

ab _ babc _ ab _ b _ bcb _ b

Let's check the given options –

First option: c b c a a

The series becomes ab c babc b ab c b a bcb a b

The pattern in the series becomes ab c b /abc b / ab c b / a bcb / a b

Second option: c a b a c

The series becomes ab c babc a ab b b a bcb c b

There is no pattern in the above series.

Third option: a b c b a

The series becomes ab a babc b ab c b b bcb a b

There is no pattern in the above series.

Fourth option: a c a c a

The series becomes  ab a babc c ab a b c bcb a b

There is no pattern in the above series.

Hence, the first option is correct.