在线等达人做几道英语选择题

在线等达人做几道英语选择题The policemen hurried into the station_____they heard the gunshot. A.immediately B.at once C.since D.then When the poor man first set_____in America,he didn't know what the future might have in_____ for him. A.his foot,the store B.a foot,the store C.foot,store D.feet,stores This hi-tech district,____many famous universities,is now the center for Hefei's science and technology. A.based in B.the home for C.base for D.home to 最好能解释下为什么这么做!谢谢