根据所给要求，改写下列句子，每空格限填一词。
1. Lily had a good time during her stay in Beijing. (改为否定句)
Lily ________ ________ a good time during her stay in Beijing.
2. We have a class meeting once a week. (对划线部分提问)
_________ _________ do you have a class meeting?
3. Many countries make laws to stop smoking in public. (改为被动语态)
Laws _________ _________ by many countries to stop smoking in public.
4. The river pollution is serious in our country today. (改为感叹句)
_________ _________ the river pollution is in our country today!
5. Robert is so short that he can't yet reach the pears on the table. (改为简单句)
Robert isn't _________ _________ to reach the pears on the table.
6. I can't give you better advice than that. (保持原句意思)
I can _________ give you _________ advice.
7. Bill didn't go to bed until he finished writing the letter at 11:45 last night. (保持原句意思)
Bill _________ _________ until he finished writing the letter at 11:45 last night.