电气设备和电动工器具应用橡胶电缆，外壳必须（）。
A.接地
B.接零
C.绝缘
D.保护
参考答案：A
—Sorry, I’m late. Has the meeting begun?
—It doesn’t matter. The meeting for several minutes.
A．has just begun
B．has just been over
C．has just been on
D．has just ended
用于治疗重症肌无力的药物是
A．新斯的明B．尼古丁C．东莨菪碱D．山莨菪碱E．毛果芸香碱
