Concept:The idiom "have a finger in every pie" means being involved in many different activities at the same time.
Explanation:Someone who has a finger in every pie takes part in a wide range of activities or affairs.
The sentence says hardworking students "must not" do this at school.
The phrase "must not" expresses strong advice or prohibition, not a statement of fact.
So the sentence warns that hardworking students should avoid taking part in most school activities.
Option A matches this meaning because it says they must not have a role in most activities.
Option B is wrong because it changes the meaning to participation in all activities.
Option C is wrong because it is a statement of fact, not advice.
Option D is wrong because asking others to participate is not mentioned in the sentence.
Answer:A. Hardworking students must not have a role to play in most activities in the school.