Answer:
D popularity
Step-by-step explanation:
This is one of those questions where the answer is inferred. What makes the process so long is never really addressed. But what is said is that the candidates are chosen by the primaries. That means exposure before the actual election takes place.
A: There's nothing about seeking a staff. Not A
B: I can't say why this is wrong. It simply is not the main idea. Responsibility is something all candidates are assumed to have.
C: Another term I'm not sure why it is used. It means awards. It's only indirectly talked about. This paragraph is about the process, not the rewards.
D: The Candidates are looking for the popular vote. They have to be nominated before they can be elected president. That's what the popular vote means.