After work I went to the box office to buy the tickets for Kungfu Panda 2, only to be told there was ______ left. A.nothing B.none C.no one D.neither 答案:B“神舟号”载人航天器中宇航员所在的轨道和返回仓都是密封的,宇航员吸入氧气、呼出二氧化碳,如果二氧化碳浓度过高,会使宇航员困乏,呼吸频率加快,严重的还会窒息,为解决此问题,应在航天仓中加入( )A.Na2O2B.Na2CO3C.NaOHD.高压氧气瓶