题目

Helen ______ her keys in the office so she had to wait until her husband ______ home. A . has left; comes B . left; had come C . had left; came D . had left; would come 答案：C下列表示对应化学反应的离子方程式正确的是（　　）A．氯化铝溶液中加入过量氨水：Al3++4NH3?H2O=AlO -2+4NH +4+2H2OB．过氧化钠与水反应制备氧气：Na2O2+H2O=2Na++2OH-+O2↑C．硫酸亚铁溶液被空气中氧气氧化：4Fe2++O2+2H2O=4Fe3++4OH-D．“84消毒液”（含NaClO）和“洁厕灵”（含盐酸）混合：ClO-+Cl-+2H+=Cl2↑+H2O