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问题 多项选择题

某站点电源设备测得交流输入三相电压如下：UAN=210V，UBN=223V，UCN=75V，对此合理的解释是（）。

A、C相缺相

B、零线中断或接触不良造成相不平衡

C、三相负载严重不平衡

D、交流电网不稳定

答案

参考答案：B, C

阅读理解
Simon is reading his e-friend’s views on the net. Let’s have a look!
Topic
Writer
Time
Reply/Click
I don’t like to have training classes at weekends. But my mother says I should have, or I can’t keep up with others.
Mike
21:32
21/05
8/65
I like playing the piano. But my parents let me practice it for a long time every day, so I begin to hate playing the piano.
Kitty
22:20
22/05
4/32
I watched the two matches last night. I slept very late, but I’m feeling energetic today, because the England won.
Nick
18:46
23/05
26/132
The football match on CCTV-5 last night was very bad. The striker(前锋) missed all the chances. He made my favorite team lose the game.
Jim
21:25
23/05
11/28
小题1:Whose topic was read by the most students?
A．Mike’s.B．Nick’s.C．Kitty’s.D．Jim’s.
小题2:Why does Kitty begin to hate playing the piano?
A．Because she has no time to play it.
B．Because she can’t watch matches.
C．Because she has to play it for a long time every day.
D．Because she can’t keep up with others.
小题3:Which of the following is NOT true?
A．Mike has training class at weekends.
B．Kitty doesn’t like playing the piano at all.
C．Nick is a fan of the England team.
D．Jim is not pleased with the striker.
查看答案
单项选择题

划分流体运动状态的基本依据是( )，用Re表示。

A．雷诺数

B．临界数

C．内径数

D．平均数
查看答案