普通型携带式电气设备测量表，只准在瓦斯浓度（）以下的地点使用。
A.0.5%
B.1%
C.1.5%
D.2%
参考答案：B
Many teens don't get enough sleep because they have too much homework to do, which ________ them up at night.
A．makes
B．breaks
C．turns
D．keeps
在异步电动机直接起动电路中，熔断器的熔体额定电流应取电动机额定电流的（）倍。
A．1～1.5
B．1.5～2
C．2.5～4
D．4～7
