This question presents a sentence, part of which or all of which is underlined. Beneath the sentence, you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise, choose one of the others.
In presidential campaigns, a caucus is a system of local gatherings whose voters decide which candidate to support, and select delegates for nominating conventions, while a primary is instead a statewide voting process where voters cast secret ballots for their preferred candidates.