题目

There ____ great changes in our hometown in the last few years . A. have had        B.have been        C.were         D.has been 答案：B下列现象或事实不能用同一原理解释的是(   )A．浓硝酸和氯水用棕色试剂瓶保存 B．硫化钠和亚硫酸钠固体长期暴露在空气中变质 C．Cl2和SO2都能使品红溶液褪色 D．SO2和Na2SO3溶液都能使溴水褪色