Question

if a question is possible to study, that means it is
irrelevant to the topic
unfocused on a goal
feasible to study
asking for an opinion

Explanation:

The key is to understand the meaning of each option. "Relevant to the topic" is about connection, "unfocused on a goal" is about lack of direction, "asking for an opinion" is about subjective view. "Feasible to study" directly relates to the idea of being possible to study.

Answer:

feasible to study