Select the letter-cluster from among the given options that can replace the question mark (?) in the following series.
KRO, PWT, UBY, ?
Answer & explanation
Correct answer: option 3

Explanation:
KRO, PWT, UBY, ?
The logic followed here is :
K → (+5) → P → (+5) → U → (+5) → Z
R → (+5) → W → (+5) → B → (+5) → G
O → (+5) → T → (+5) → Y → (+5) → D
So, the letter-cluster that replaces the (?) to complete the series is "ZGD"