Me i don’t understand how to do this

Well, if you look closely at the underlined words, you'll see either one doesn't belong or all of them do, in which case you would chose no error. For example, number 215., the answer would be D, because its is possessive, but it's is the combination of it is. Hope this helps! ^W^

Delegates: representatives who cast votes at a political party's national convention. binding: if a primary or caucus is “binding” that means the delegates won in that contest are legally bound to vote for a particular candidate at the parties national convention.a primary is a preliminary election used to determine a party's nominee for a specific office. the winner of the party's caucus, or primary, wins the party nomination for that state. then the delegates meet at their party's national party convention, which is a formal gathering of all party delegates from all states.