Select the letter-cluster from among the given options that can replace the question mark (?) in the following series.
XJ, AG, DD, GA, ?
Answer & explanation
Correct answer: option 2

Explanation:
XJ, AG, DD, GA, ?
The logic followed here is :
X → (+3) → A → (+3) → D → (+3) → G → (+3) → J
J → (-3) → G → (-3) → D → (-3) → A → (-3) → X
So, the letter-cluster that replaces the (?) to complete the series is "JX"