Correct Answer: zyxkx

Solution : Given:
xy_kx_zk_yzkxyz_ _

To fill the series we have to divide the series – xy_k / x_zk / _yzk / xyz_ / _
Let's check each option –
First option: zyxkx; xy z k / x y zk / x yzk / xyz k / x (xyzk is repeated in the series.)
Second option: zykxz; xy z k / x y zk / k yzk / xyz x / z (No repeated pattern has been found.)
Third option: zkxyk; xy z k / x k zk / x yzk / xyz y / k (No repeated pattern has been found.)
Fourth option: zxykx; xy z k / x x zk / y yzk / xyz k / x (No repeated pattern has been found.)

So, the series becomes→xyzkxyzkxyzkxyzkx. Hence, the first option is correct.