Select the letter-cluster that can replace the question mark (?) in the following series.
GHB, LMG, PQK, ?
Answer & explanation
Correct answer: option 1

Explanation:
GHB, LMG, PQK, ?
The logic followed here is :
G → (+5) → L → (+4) → P → (+3) → S
H → (+5) → M → (+4) → Q → (+3) → T
B → (+5) → G → (+4) → K → (+3) → N
So, the letter-cluster that replaces the (?) to complete the series is "STN"