单项选择题 —We took a taxi and arrived at the station an hour earlier. —You ______ a taxi. Time was enough for you to go there by bus. A．neednt take B．neednt to take C．neednt have taken D．dont need take

单项选择题 功能性分流是指( ) A．肺动-静脉短路开放 B．部分肺泡V/Q比率增高 C．死腔气量增多 D．解剖分流增加 E．部分肺泡V/Q比率降低

单项选择题 9．1molH2O的质量为( ) A．18 B．18g C．18mg D．18kg