氧气浓度小于18%的情况下,过滤式自救器仍可用于自救。
参考答案:错
I have ________ to do today. [ ]
A. anything important
B. something important
C. important nothing
D. important something
每()应对刮板输送机液力偶合器,过滤槽,链轮和拨链器等进行轮换检修1次,每()应对电动机和减速器进行1次全面检修。