1. You must not knock the door before you enter my room.
2. You must not do it at once.
3. You must not be a teacher.
Are the sentences meaningful and natural?
You must not knock on the door before you enter my room. Native speakers never say 'knock the door'. English learners say it a lot.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
!. You must not knock on the door before you enter my room. Native speakers never say 'knock the door'. English learners say it a lot.
2. . You must not do it at once. This is not natural, and I'm not sure what you mean.
3. You must not be a teacher. This is natural, but the meaning depends on the context in which it is said.
Clive