电弧最初的游离方式是（）。
A、热电发射
B、高电场发射
C、碰撞游离
D、热游离
参考答案：A
— One's week's time has been wasted.
— I can't believe we did all that work for _______. [ ]
A. something
B. none
C. nothing
D. anything
什么是“社会人”假设
