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).