you must not draw on the blackboard.

你不许在黑板上画画 再问： 谢谢 那 you must return the books in time ？ 再答： 你必须及时返还那些书再问： you must not step the grass ? 再答： 你不许踩草地再问： 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