《煤矿安全规程》规定，人员上下的主要倾斜井巷，垂深超过（）时，应采用机械运送人员。
A.50m
B.60m
C.65m
D.70m
参考答案：A
The MCA Youth has expected more participants to join the trip to the Expo 2010 Shanghai ________ from May1 to October31 this year to explore the world.
A．being held
B．to be held
C．having been held
D．held
当示波器的输入耦合选择（开关）置于直流耦合（DC）位时，适合于观察（）的信号。
A.变化缓慢
B.变化迅速
C.交流类
D.尖脉冲类
