根据短文内容, 选择正确的答案填空。

It's Sunday today. Lucy is reading a story. The story is about the cat and the mice. The cat is a police officer. The mice often steal(偷) things from people's houses. The cat is very angry with the mice. So he often chases them. The mice are afraid of the cat. One day, the cat is ill. He goes to the hospital. The doctor says he should have a good rest and do more exercise. After that, the cat takes exercise every day and becomes strong again.