题目

Only after my friend came, __________________. A . did the computer repair B . he repaired the computer C . was the computer repaired D . the computer was repaired 答案：CA、B、C、D、E均为初中化学常见的纯净物，它们之间在一定条件下有如下转化关系（部分生成物已略去）．（1）若D和E 是同种物质，则②的化学方程式为2CO+O2 点燃 . 2CO22CO+O2 点燃 . 2CO2；（2）若A和C是同种物质，则①的化学方程式为CaCO3 高温 . CaO+CO2↑CaCO3 高温 . CaO+CO2↑．