题目

 —My computer ____start, no matter how hard I try.    —It might have crashed.    A. won't   B. shouldn't   C. mustn't        D. wouldn't 答案：A（4分）利用氧化还原反应原理配平⑴ 　NH3 +   　O2     NO +     H2O　　 ⑵　FeSO4 +　KNO3 +　H2SO4 = 　K2SO4 +　Fe2(SO4)3 + 　NO↑+　H2O