阅读下面短文掌握大意，然后从题中所给的四个选项中选出一个最佳选项。

Mr. Miller lives alone (独自生活). His son and daughter live in another city, so they can't come to visit him very often. Mr. Miller is getting very 1 and it's very hard for him to 2very long, but he has a little 3. The dog needs two walks every day. Mom asks me if I'd like to 4 Mr. Miller. I say yes 5.

Every morning before school, I go to Mr. Miller's house and 6 the dog to the park to have a quick walk. Then I walk the dog back home. After that, I go to 7.

In the afternoon after school, I have more free 8, so I take the dog to the park and play tennis ball 9 him. I throw (扔) the ball out. He runs to catch it and brings it back to me. He can always have lots of fun.

Mr. Miller is very 10 because I can come to help him, and I feel happy, too!