通常把产生能量的能量源或拥有能量的能量载体作为（）。
A．第一类危险源
B．第二类危险源
C．第一类和第二类危险源
D．危险源
参考答案：B
. —I hear our manager wants to hire a new secretary. — _______?
A．What’s up
B．Who does he think he is
C．Does he have anyone in mind
D．Does he have anything on his mind
通常情况下能共存，且能用浓硫酸干燥的一组气体是[ ]
A．H2 O2 N2
B．O2 NO NO2
C．H2 N2 NH3
D．NH3 HCl NO2
