自行车是我们的常用代步工具,不少同学每天都是与它结伴而行的。也许同学们会觉得“自行车是怎样前进的”这个问题太简单了:“因为人用力蹬车,所以车向前进。”确实,我们每天在生活中就这么日复一日地蹬车前进,在不少同学看来, Bicycles are our common means of transportation. Many students go hand in hand with it every day. Perhaps the students will feel that the question “How bicycles move forward” is too simple: “Because people drive cars hard, they move forward.” Indeed, every day in our lives, we move on cars day after day. Many students think that