Correct Answer: CEADFACEAE

Solution : Given:
AA_D_F_AC_E_A_ _D_F_ACD_F

To fill the series we have to divide the series – AA_D_F / _AC_E_ / A_ _D_F / _ACD_F

Let's check each option –
First option: CAFDFAACEE; AA C D A F / F AC D E F / A A A D C F / E ACD E F (No repeated pattern has been found)
Second option: CEADFACEAE; AA C D E F / A AC D E F / A A C D E F / A ACD E F (AACDEF has repeated in the series)
Third option: ACDAFACEAE; AA A D C F / D AC A E F / A A C D E F / A ACD E F (No repeated pattern has been found)
Fourth option: CEAFDACEAC; AA C D E F / A AC F E D / A A C D E F / A ACD C F (No repeated pattern has been found)

So, the series becomes→AACDEFAACDEFAACDEFAACDEF. Hence, the second option is correct.