题目

 For some time now, Chinese people, under the leadership of CPC, ______ the contents of the Scientific Development Theory in the course of practicing socialism in China. A. had been improving  B. have been improving C. were improving D. improved 答案：B1898年，居里夫人发现了放射性元素镭（Ra），因而获得诺贝尔化学奖，已知镭是周期表第7周期IIA族的元素，下列关于镭说法不正确的是（ ）A．在化合物中呈现正二价B．单质能与水剧烈反应放出氢气C．碳酸盐难溶于水D．氢氧化物呈两性