单句语法填空。
1. By the time he got home, his wife ______ (do) all the housework.
2. In the United States, lunch _______ (offer) to students for free at school.
3. The first step towards _______ (protect) the environment is to live a "low-carbon" lifestyle.
4. While I ______ (sweep) the floor yesterday, the telephone rang.
5. The audience are requested _______ (show) their tickets when they enter the cinema.
6. They _______ (eat) up all the food, but they still feel hungry.
7. We meet each other _______ (frequent) in this hotel.
8. I prefer basketball _______ football.
9. By reading we can ________ (rich) our vocabulary and improve our English.
10. My friend is growing _______ tired of English words that he wants to give it up.