You mustn't talk in the class.

-You mustn't talk in the class.

I must not get out of the class without permission

-I must not get out of the class without permission

I must help the companions

-I must help the companions 

we mustn't use the cell phone in class

-we mustn't use the cell phone in class

I mustn't fight in the school

-I mustn't fight in the school

not paint in restrooms

-not paint in restrooms

i must use the uniform

-i must use the uniform 

I must comply with the regulation

-I must comply with the regulation

I must not tread the gardens

I must not tread the gardens

I must not eat in hour of class

 - I must not eat hour of class