题目

—Can I have a talk with you at about 4 this afternoon，Mr Black?—All right，I ________from a conference by then.I will be waiting for you. A . will have come back B . will come back C . have come back D . will be coming back 答案：A下列实验方案设计正确的是（　　）A．分解高锰酸钾制氧气后，残留在试管内壁上的黑色物质可用稀盐酸洗涤B．失去标签的硝酸银溶液、稀盐酸、氢氧化钠溶液、氯化铝溶液，可以用碳酸铵溶液鉴别C．检验溶液中铵根离子可以直接加热溶液，产生使湿润的红色石蕊试纸变蓝的气体D．检验从火星上带回来的红色物体是否是Fe2O3的操作步骤为：样品→粉碎→加水溶解→过滤→向滤液中滴加KSCN溶液