题目

用化学符号填空： (1)3个铵根离子         ； (2)氧化钙中钙元素为+2价         ； (3)将湿润的蓝色石蕊试纸投入二氧化碳的瓶中，发生的化学反应方程式         ； (4)节能日光灯能使用很长时间，主要是日光灯内充有          。 答案：根据句意，用括号中所给动词的正确形式填空，词数不限。【1】 —Who (mop) the floor at this time yesterday? —My mother. 【2】 My mother often told me (not throw) rubbish everywhere when I was young. 【3】The price of the Renminbi (RMB) yuan against the U.S. dollar used to keep (rise).【4】 Daniel always (have) pity on those people who lose their families in disasters.【5】 I hope our school (provide) us students with a better environment next term.