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.