Respuesta :
Answer:
D. vital: of primary importance
Explanation:
The helpers' duty or function in the student's campaign was crucial and of the utmost importance for her to win the election and become student body president. In that respet, the the new president considers that her collaborators' ideas, beliefs and hard work were decisive in her winning of the election.
The rest of the alternatives are incorrect because they do not accurately describe hard work and ideas.