麻烦把这两段改成过去式,

Crowns were an important part of the circus。They were funny and they made the audience laugh。They were also useful to the circus in other ways。
Many performers needed to be in different shows。The crown shows gave them time to change costumes。Also,performers could hurt themselves or other acts could go wrong。At these times,the crowns performed for the audience,so the show could continue。