A、Biology. B、Economics. C、Geography. D、Computer. A在自然课上，学生可以学到生物、化学和物理方面的知识。

In American high schools, most students take English, science, maths and history. These are basic courses and each course is as useful as the others. In English class, the students study grammar and read famous literature. In science class, they study biology, chemistry or physics. History is more interesting to some students because they learn about important events and places in the United States. Students take other courses too. These are electives. Some of them are music, home economics and computer science. Students don’t have to take all of these courses. Some study music because they feel it is more enjoyable. Some study computer science because they think it is more practical. In each class, teachers give students exams. Some exams are more difficult than others, but a good student can always do well.