二氧化碳、氧气、氧化汞中含有相同的 [ ]
A.氧气
B.氧元素
C.氧分子
D.两种元素
答案：B
The speech delivered by the mayor of Shanghai on the opening ceremony of the World’s Swimming championship left me a deep ___________．
A．expression
B．permission
C．opinion
D．impression
What is the main reason to slush a wire rope?（）
A.Keep the wire soft and manageable
B.Lubricate the inner wires and prevent wear
C.Prevent kinking
D.Prevent rotting
