Correct Answer: ORKPLYO

Solution : Given:
PRKY_LDP_ _YOLD_RKYO_DPRK_ _LD

To fill the series we have to divide the series – PRKY_LD / P_ _YOLD / _RKYO_D / PRK_ _LD

Let's check each option –
First option: ORKLPOD ; PRKY O LD / P RK YOLD / L RKYO P D / PRK OD LD (No repeated pattern has been found)
Second option: ORPKYLP ; PRKY O LD / P RP YOLD / K RKYO Y D / PRK LP LD (No repeated pattern has been found)
Third option: ORPLKYO ; PRKY O LD / P RP YOLD / L RKYO K D / PRK YO LD (No repeated pattern has been found)
Fourth option: ORKPLYO ; PRKY O LD / P RK YOLD / P RKYO L D / PRK YO LD (PRKYOLD is repeated in the series)

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