题目

Air bags for cars were invented _____ lives. Without them more people would be injured in car accidents.        A. saving                  B. saved                    C. to save                   D. to have saved 答案：C实验室用高锰酸钾制氧气大致分为下列几步：其正确操作顺序为①组装、连接仪器；②给药品加热；③检查装置的气密性；④装入药品于试管中；⑤用排水法收集氧气；⑥从水中取出导管并熄灭酒精灯A．①③④②⑤⑥B．①②③④⑤⑥C．①③②⑤④⑥D．③④②⑤⑥①