如图所示,粗细均匀的棒一端搁在地上,另一端与支点O 连接。试作出地面对棒的支持力的力和棒所受重力G的示意图。(在答题卡相应的位置上画出原图并作答)
— Is Tom a student with good manners?
— I don't think so. In fact, he is ____ but polite. [ ]
A. something
B. anything
C. nothing
D. everything
变压器的过激磁保护反应的是电压与()的比值。