“数量及单位”栏应填（）。
A．50463kg
B．50200kg，100000m
C．100000m
D．50463kg，100000m
参考答案：B
哪一种频率的交流电危害性最大
A．50—60Hz
B．60—100Hz
C．100—150Hz
D．150—200Hz
E．＞200Hz
One day while Mr. King was working, he had a(an)（）and his left leg was badly injured.
A.business
B.accident
C.matter
D.event
