Select the letter-cluster that can replace the question mark (?) in the following series.
qDx, nHs, kLn, hPi, ?
Answer & explanation
Correct answer: option 3

Explanation:
qDx, nHs, kLn, hPi, ?
The logic followed here is :
q → (-3) → n → (-3) → k → (-3) → h → (-3) → e
D → (+4) → H → (+4) → L → (+4) → P → (+4) → T
x → (-5) → s → (-5) → n → (-5) → i → (-5) → d
So, the letter-cluster that replaces the (?) to complete the series is "eTd"