Question

If you write a sentence with an unclear antecedent, it means you used

Answer 1

Let's think of an example here:

At the party, John cooked, James played the music and Jacob brought his girlfriend. He was very excited, as it was the first time he did it. Here the unclear antecedent is "he".

So I used a pronoun that can refer to more than one thing: it could refer to any of the men.