please help me correct the right choice so that the pronouns agree with the antecedents.

1- Each of the horses stood on ( its, their ) hind legs.

2) Neither Bob nor Kevin wore ( his, their ) old clothes.

3) Everybody did ( his, their ) best on the exam.

4) Didn't any of the girls return ( her, their ) books to the library?

5) All of the hikers put ( his, their ) boots on.