Correct Answer: CDAAC

Solution : Given:
D_BA_CB_DCB_D_BA

To fill the series we have to divide the series – D_BA / _CB_ / DCB_ / D_BA

Let's check each option –
First option: CDAAC; D C BA / D CB A / DCB A / D C BA (DCBA is repeated)
Second option: DBCAC; D D BA / B CB C / DCB A / D C BA (No pattern is repeated)
Third option: DCBCA; D D BA / C CB B / DCB C / D A BA (No pattern is repeated)
Fourth option: CBDCA; D C BA / B CB D / DCB C / D A BA (No pattern is repeated)

So, only the first option follows a pattern. Hence, the first option is correct.