凡在距地面（）m以上地点工作都应视为高处作业。
A.1.5
B.2.0
C.2.5
D.3
参考答案：B
In relation to the law of agency, explain the ways by which an agency may come into existence. (10 marks)
催化剂烧焦时，系统中氢含量应小于（）。
A、0.1%vol
B、0.2%vol
C、0.3%vol
D、0.5%vol
