题目

You______have made great progress since two months ago. A.sure                         B.are sure of                C.certain                      D.make sure 答案：Ａ 解析: sure 副词，确实，当然。例如：He sure is tall.他的确很高。除去括号内杂质所用试剂和方法不正确的是（　　）A．Cu（Fe）----加盐酸，过滤B．NaCl溶液（碘）----CCl4，萃取、分液C．Cl2（HCl）----饱和食盐水，洗气D．CO2（HCl）----饱和碳酸钠溶液，洗气