Select the option that is related to the third letter-cluster in the same way as the second letter-cluster is related to the first letter-cluster.

DBZ : WUS :: PNL : ?

IGE

Explanation:

DBZ : WUS :: PNL : ?

The logic followed here is :

D → (-7) → W → (-7) → P → (-7) → I 

B → (-7) → U → (-7) → N → (-7) → G 

Z → (-7) → S → (-7) → L → (-7) → E

So, the letter-cluster that replaces the (?) to complete the series is "IGE"