Correct Answer: CEDEFDCECF

Solution : Given:
D_C_FE_CC_ _E_C_EF_D_CE_E

To fill the series, we have to divide the series – D_C_FE / _CC_ _E / _C_EF_ / D_CE_E
Let's check each option –
First option: ECDEFDCECF; D E C C FE / D CC E F E / D C C EF E / D C CE F E (No repeated pattern has been found.)
Second option: CEDEFCDECE; D C C E FE / D CC E F E / C C D EF E / D C CE E E (No repeated pattern has been found.)
Third option: CEDFEDCECE; D C C E FE / D CC F E E / D C C EF E / D C CE E E (No repeated pattern has been found.)
Fourth option: CEDEFDCECF; D C C E FE / D CC E F E / D C C EF E / D C CE F E (DCCEFE is repeated in the series.)

So, the series becomes→DCCEFEDCCEFEDCCEFEDCCEFE. Hence, the fourth option is correct.