题目

 ----Have you completed the project?    ----I’m sorry to tell you that we ______ it when we found how much it _____.    A. have abandoned, costs                   B. abandoned, cost  C. had abandoned, cost                     D. abandoned, would cost 答案：D现有铁、硫酸、碳酸钠、氢氧化钠、氯化钙五种物质，试选用上述物质按下列要求写出化学方程式（1）有气体生成的置换反应______（2）有气体生成的复分解反应______（3）有沉淀生成的复分解反应______（4）既是复分解反应又是中和反应______．