你举一个例子说明你的讲法，我已经用牛顿的例子解释很清楚了？

来源: fourwaves 于 2019-08-25 12:17:41 [旧帖] [给我悄悄话] 本文已被阅读：次

WENXUECITY.COM does not represent or guarantee the truthfulness, accuracy, or reliability of any of communications posted by other users.