玻璃电极上有油污时，可用无水乙醇、铬酸洗液或浓H2SO4浸泡、洗涤。( )
参考答案：错
— Is John in the office?
— I didn't see ____ there.[ ]
A. anyone
B. someone
C. everyone
D. each one
露天开采中，运输费用约占开采总成本费用的（）%。
