用括号内动词的正确形式填空。
1. The sun (go) down earlier in winter than in summer.
2. I _____ (write) a letter to my pen-friend yesterday.
3. Miss Gao _____ (teach) the students to sing an English song now.
4. The Greens _____ (stay) at home next Friday.
5. He _____ (tell) to return his book to the library yesterday morning.
6. I' d like you _____ (meet) my parents tomorrow evening.
7. There _____ (be) a lot of great changes in China since 1949.
8. The fridge is used for _____ (keep) food fresh.