-Which would you like, a cup of tea or a glass of milk?- ______. I think I'll just have a glass of water.
A: Both
B:Neither
C:None
D:Either
电子以初速度v0沿垂直场强方向射入两平行金属板中间的匀强电场中,现增大两板间的电压,但仍使电子能够穿过平行板间,则电子穿越平行板所需要的时间( )