change these sentences into passive voice.but DON'T use by. 被动语态 不用by
change these sentences into passive voice.but DON'T use by.
1.People must return library books within three weeks.
2.You should keep all medicine in a locked cupboard.
3.Customers cannot exchange goods without a receipt.
4.Patients should not take these pills more than twice a day.
5.They may hoist the typhoon signal NO.8 later today.
6.We will not allow children wearing school uniforms into Internet cafe.
7.Can people use this shampoo every day?
8.Students must not borrow this equipment without permission.
9.The government should prohibit smoking in public.
10.People can buy vitamin pills at a chemist's.