题目

   鉴别NO2和溴蒸气的方法可选用 …（    ）     A．通入蒸馏水中观察颜色变化    B．通入AgNO3溶液中观察沉淀的生成    C．用湿润的淀粉碘化钾试纸接近气体    D．分别通入NaOH溶液观察颜色变化    答案：   解析：Br2(g)通入水中，仍有颜色，通入AgNO3（aq）中会生成淡黄色沉淀；NO2也可使湿润的淀粉碘化钾试纸变蓝，NO2和Br2(g)遇NaOH都呈无色。  答案：AB__________ without friends __________ the most difficult challenge for Chuck while living on the island.A. How did he survive; were B. How he survived; wereC. How did he survive; was D. How he survived; was