进入反应器内工作时，一定要采取声波吹灰器误启动措施，如切断声波吹灰器仪用空气。
参考答案：对
— Who is knocking at the door?
— _______. [ ]
A. They are the children
B. There are the children
C. It is the children
D. That is the children
物质的用途和性质密切相关。下列用途主要是利用其化学性质的是[ ]
A．干冰做制冷剂
B．金刚石作装饰品
C．铜丝作导线
D．氢气作高能燃料
