CRH2型动车组一、二级检修作业时，一级检修中高压受电弓上推力和下降力之差不应超过（）。
A、30N
B、25N
C、20N
D、40N
参考答案：C
在项目输出的时候，视频格式有（）。
A.MP3
B.DV AVI
C.MPEG
D.QuickTime
E.MicrosoftAVI
A．Many people who are in need work in it.
B．The hospital blood is mainly provided by it.
C．Anyone can get help from it.
D．It covers nearly the whole world.
