Choose the right answer according to the passage.
American schools are quite different from those in China. In America, at the beginning of the term, students must select their subjects and teachers first
Selecting is very important for your grades in America. So at the first term, don't select too many subjects, or you'll feel very nervous and it may influence your study. Then you have to ask for some teaching plans. There is some information about subjects, timetables, marks and textbooks. At the same time, you must choose the teachers. Different teachers have different teaching methods. If the teacher is called “killer” by the last grade, many students will give up choosing him. Because this kind of teacher will leave too much homework, too many exams and give too low grades.
There is another thing after you select the subjects and the teacher. How to buy textbooks makes each student feel hard. The textbooks in America are very expensive. Each one is about $30-50. In order to save money, many students buy some used textbooks, and some students usually borrow textbooks from the school library.
In class, discussing is very important. The teacher encourages you to ask questions or show your own opinions. They don't usually ask you to sit well. Instead they allow you to sit or stand everywhere you like.
的半径为1，其圆心与点 
关于直线 
对称，则圆 
