题目

 ______all  the homework assigned by the school the students have to work at it till midnight A. Completing   B. To complete     C.Having completed       D. To have completed 答案：B某同学进行的实验操作，其中错误的是A.做铁丝在O2中燃烧实验前在瓶底放一点细纱或水B.用稀硫酸和碳酸钙制取二氧化碳气体C.做有关气体的实验前要先检查装置的气密性D.用酒精喷灯做木炭还原氧化铜的实验