Correct Answer: WUQK

Solution : Given:
_XYZU_UUSR_PQOM_

To fill the series we have to divide the series – _XYZ \ U_UU \ SR_P \ QOM_
Let's check each option –
First option: UVSY; U XYZ \ U V UU \ SR S P \ QOM Y (No repeated pattern has been found)
Second option: WABC; W XYZ \ U A UU \ SR B P \ QOM C (No repeated pattern has been found)
Third option: WOVK; W XYZ \ U O UU \ SR V P \ QOM K (No repeated pattern has been found)
Fourth option: WUQK; W XYZ \ U U UU \ SR Q P \ QOM K (The first letter is decreased by 2, the second letter is decreased by 3, the third letter is decreased by 4 and the fourth letter is decreased by 5 in the series)

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