分组交换服务的计费原理与电路交换服务的计费原理是不同的，分组交换服务是基于（）计费。
A.流量
B.时间
C.功能
D.速度
参考答案：A
—Why did John asked me about the problem?
—______, he tried to find a better way to settle it.
A. Not to be satisfied
B. Don't satisfy
C. Not being satisfied
D. Not satisfied
甲、乙两同学各用2N的力在水平桌面上沿相反方向拉一弹簧测力计，则弹簧测力计的示数是______N，弹簧测力计所受合力是______N．
