you must not draw on the blackboard.

谢谢 那 you must return the books in time ？

you must not step the grass ?

you must put back the books after you have read them . you must not talk to drivers when the bus is moving . youmust clean the classroom every day. you must not jump the queue when you wait in line for the bus . you must put away the balls after you have used them. 这些那 ？帮帮我