电阻一电抗移相原理构成的复式电流滤过器。当调整电阻等于（）时，则为负序电流滤过器。
A、2Xm；
B、2Xm；
C、Xm；
D、3Xm。
参考答案：C
May 12th，2008 is a special day，________, I think，that will be remembered by the Chinese forever.
A．one
B．it
C．which
D．that
---Let’s have a further talk.
---Sorry, I don’t have time. My report is due on Friday and I am in a race ________ time.
A．over
B．in
C．on
D．against
