用所给单词的适当形式，完成句子。

1. My shoes are worn out. I will have them _____ (mend) this afternoon.

2. When I got to the cinema, the tickets _____ (sell)out.

3. How many books _____ you _____ (read) during the past two weeks?

4. _____ (chemical) is my favorite subject at school.

5. He explained the question again to make himself _____ (understand).