绝缘油在电弧作用下产生的主要气体是（）。
A.甲烷、乙烯
B.氢、乙炔
C.一氧化碳
D.二氧化碳
参考答案：B
– What place is it?
---Haven’t you found out we ______back where we ______?
A．were; had been
B．are; were
C．were; have been
D．are; had been
二氧化碳有功也有过，请说出其中两条．功是①______②______过是①______②______．
