【简答题】C语言标识符的第一个字符只能字母或______
【单选题】We were forced to our office from downtown New York to suburbs because the rent in big city was too high.
【单选题】_____ in the fog, we were forced to spend two hours in the woods.
【多选题】以下属于4.3遇水释放易燃气体的物质是( )
【单选题】The spring floods had washed away the bridge, we were forced to take a ______ route.