chuyển sang câu bị động
1) We must keep this talk secret
2) We shouldn't warn the director of this risk
3) You mustn't leave this door open under any circumstances
4) We can understand this question without any difficulty
5) You should change the battery of the remote control
6) We must wash this kind of cloth in warm water only
7) We ought to deal with the problem before people talk about it
8) You mustn't touch this button while the experiment is in progress
9) Can they repair the machine in two days
10) They couldn't find the man anywhere