阅读理解。
The class in America is almost the same as that in China. But something is different.
(1) 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（重复）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.
(2) You mustn't be absent on a test day. If you are seriously ill, call and let the teacher know you will not
be there for the test. If your teacher allows a make-up test （补考）, you should take the test in one or two
days after you go back to school.
(3) Be on time! It is impolite to be late. If you come in late, be sure to do it quietly. Take your books out
of your bag after you enter the room. Then go to your seat and sit down quietly. In the US, you needn't
knock before you come into the classroom.
(4) If you have to leave during the class, do it quietly, too. There is no need to ask the teacher's agreement
（同意）.
阅读短文，判断正（T）误（F）。
( ) 1. When a teacher asks you a question, you should repeat the question.
( ) 2. Though a student is too sick to take the test, he is not allowed to take a make-up test.
( ) 3. It's impolite for a student when he/she gets to school late.
( ) 4. In the US, you need knock before you come into the classroom.
( ) 5. One can leave the classroom without the teacher's agreement.
＝b，即c2＝a2＋b2，故△ABC一定是直角三角形．