一定温度下,向a L密闭容器中加入2mol NO2(g),发生如下反应:2NO22NO + O2,此反应达到平衡状态的标志是( )
My friend showed me round the town, ______ was very kind of him.
They use computers to keep the traffic _______ smoothly.
If you leave the club, you will not be_____back in .
What I need is_____ book that contains ______ABC of oil painting.
Jenny nearly missed the flight______ doing too much shopping.