在什么情况下采用三相差动保护?什么情况下采用两相差动保护?

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问题:

在什么情况下采用三相差动保护?什么情况下采用两相差动保护?

考点:用电检查员考试用电检查员(综合练习)用电检查员(综合练习)题库
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改错题。

     After shopping, Mother and I went to a restaurant for lunch. I notice Mother looking at a nearby table

occupy by an elderly woman and young couple. They are silently, and it was clearly that things were not

going well. As we left, Mother stopped on their table. "Excuse me," she said, put her arm around the

unhappy old woman. "You remind me so many of my mother. May I hug (拥抱) you?" The woman smiled

happily as she accepted to it. After we left, I said, "That was very nice of you, Mother. So I didn't think she

looked like Grandma." "Neither did me." said Mother cheerfully.

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据国家统计局2008年1月24日公布的2007年国民经济运行数据,经初步核算,2007年GDP为246619亿元,增幅为11.4%.把数据246619亿元用科学计数法表示,并保留两个有效数字,其结果为(   )

A.2.5×1013

B.2.4×1013

C.25×1012

D.0.25×1014

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根据对话内容,从方框内选择恰当的句子填入对话相应的空白处,使对话完整,合乎情景(有两个多余选项)。
A: My friend Kate invited me to her birthday party . 小题1:_____________________
B: How about an album?
A: 小题2: ___________________________ How much is an album?
B: 小题3: ___________________________
A: That’s too expensive . I don’t have enough money for it.
B: Oh.小题4:________________________
A: No, no. She doesn’t like cats.
B: I see. What about a scarf?
A; 小题5:_________________
B: Does she like flowers? Maybe flowers are wonderful.
A: Great! I will buy some for her. Thank you..
A. A scarf is interesting.                      B. That sounds good.
C. Why don’t you get her a pet cat?             D. It’s too personal.
E. How can I get to her house?                 F. At least 20 dollars.
G. What should I get her?
 
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已知水的比热容是4.2×l03焦/(千克·℃),若将杯中的水倒掉一半,剩下半杯水的比热容_______(选填“变大”、“变小”或“不变”)。质量为2千克的水温度降低5℃,水放出的热量__________焦。

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成人患者出现双眼眼球突出时,多见于( )

A.眶蜂窝织炎
B.眼眶炎性假瘤
C.视神经脑膜瘤
D.甲状腺相关免疫眼病
E.眼眶静脉曲张

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