问题
选择题
You must be very tired. Why not ______ a rest.
A．stop to have
B．to stop having
C．to stop to have
D．stop having
答案
答案：A
题目分析：句意：你一定很累吧。为什么不休息一下呢？Why not do sth？为什么不做某事呢？stop doing sth停止做某事，stop to do sth停下来去做另一件事。
，水平地面给斜面体C的摩擦力为
，（
），则
