Rewrite the following sentences as required. (根据所给要求，改写下列句子，每空格限填一词)
小题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.
小题2:We have a class meeting once a week. (对划线部分提问)
_________ _________ do you have a class meeting?
小题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.
小题4:The river pollution is serious in our country today. (改为感叹句)
_________ _________ the river pollution is in our country today!
小题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.
小题6:I can’t give you better advice than that. (保持原句意思)
I can _________ give you _________ advice.
小题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.