The class in America is almost the same as that in China. But something is different.  In America, if the teacher asks you a question but you don't understand, you should put up your hand and ask the teacher to repeat it. If you don't know the answer, it is all right to tell the teacher you don't know. Then he or she knows what you need to learn.  You mustn't be _ on a test day. If you're badly ill, call and let the teacher know you will not be there for the test. If your teacher allows make-up tests  , you should take the test in one or two days after you go back to school.  Be on time! It is impolite to be late. If you come late, be sure to do it quietly. Take your books out of your bag after you go into the classroom. Then go to your seat and sit down quietly. In the US, you needn't knock at the door before you come into the classroom.  If you have to leave during the class, do it quietly, too. There is no need to ask the teacher's agreement. In the USA, if you're late for class, you  _  .
must knock at the door must go into the classroom quietly should wait for the next class outside should take your books out of your bag.