题目

Today we find that school students hardly spend much time on sports. Is it because they aren’t interested in sports? No, they often have other more important things to do. What are these important things? Examinations! They have to spend much time on all kinds of examinations at school. So many of them almost become bookworms(书呆子). Books stop them from going out for sports. Because of the pressure from their parents and teachers, the students have to work harder and spend most of their time on books. As for the students, they want to get good results so that they can improve the如图所示，平行线段有________对．