Complete the following passage with the words or phrases in the box. Each can only be used once (将下列单词或词组填入空格，每词只能填一次)


Here are some American classroom rules:
If the teacher asks a question, you are expected to give an answer. If you don’t understand the question or don’t know the answer, it’s __ __ to tell the teacher that you don’t know. Then he or she knows that you need to learn.
There is no ______ for not doing your homework. If you are absent, you should call your teachers or your classmate and _______ homework. It is your duty to find out what homework you have missed. It is not the teacher’s responsibility to tell students about the homework they’ve missed.
You must not be absent on a test day. If you are ______ill, call and let the teacher know you will not be there for the test. If you teacher allows you to take a make-up(补考), you should take the test within one or two days after _____ to class. Serious illness is the only reason for missing a test.
Be on time! It is rude to be late. Also, it disturbs other students. If you come late, be sure to do it quietly. Have your books and paper out of your bags before you enter the classroom. Then go to your seat and sit quietly. In the US it is not ____ to knock before you enter the classroom. If you have to leave during the class, do it quietly.