Select the option that is related to the fifth letter-cluster in the same way as the second letter-cluster is related to the first letter-cluster and the fourth letter-cluster is related to the third letter-cluster.
PERFECT: TCEFREP:: UPDATES:SETADPU::UNKNOWN : ?
1
UNWNKNO
2
KNOUNWN
3
OWNUNKN
4
NWONKNU