钢丝绳端部采用绳卡固定时，绳卡的间距不得小于钢丝绳直径的（）倍。
A.4
B.6
C.8
D.10
参考答案：B
按要求作图
（1）物体M是静止在一水平匀速行驶的车厢里的一木箱．如图所示，请作出M所受力的示意图．
（2）如图所示，乒乓球漂浮在水面上，请画出乒乓球受力的示意图．
Although John agreed with me on most points, here was one which he was unwilling to _____ . [ ]
A. give in
B. give off
C. give up
D. give away
