Correct Answer: cacc

Solution : Given:–
a _ ca _ ca _ caa _

Let's check the given options –

First option: caca
The series becomes a c ca a ca c caa a
There is no pattern in the above series.

Second option: cacc
The series becomes a c ca a ca c caa c
The pattern in the series becomes a c ca a c / a c caa c

Third option: caac
The series becomes a c ca a ca a caa c
There is no pattern in the above series.

Fourth option: ccca
The series becomes a c ca c ca c caa a
There is no pattern in the above series.

Hence, second option is correct.