电能质量的主要指标是()。A、电流和电压; B、有功和无功; C、频率和电压; D、

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问题:

电能质量的主要指标是()。

A、电流和电压;

B、有功和无功;

C、频率和电压;

D、电流和频率。

考点:水轮机检修工考试中级水轮机检修工中级水轮机检修工题库
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万用表测量电流应采用并接法.()

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阅读理解。

     On a hot summer day, ice-cold watermelon serves up a delicious treat. Sure, the rosy flesh (果肉) quenches your

thirst (解渴). But now there are more reasons than ever for people to reach for a slice of watermelon.

     Meet Dr. Alison Edwards. She is a scientist at the Agricultural Research Service. Scientists are people who come

up with new ideas called theories (理论). They usually do scientific research to test their new theories. That's how

they find out if a new idea is a good one, or if the new idea will bring an even better idea.

     At her lab, Dr. Edwards recently learned more about the secrets of why watermelon is good for you!

     Dr. Edwards has known for a long time that watermelon has vitamin C. But recently she learned that watermelon

also has lycopene (番茄红素). It is something that gives tomatoes and watermelon their rosy red color.

     What's so special about the lycopene in watermelon?

     Dr. Edwards says that watermelon and tomatoes both have lots of lycopene. It seems that your body can use the

lycopene from   watermelon more easily than the lycopene from raw (生 的) tomatoes.   In fact,    the lycopene from

tomatoes is more easily absorbed (吸收) inside your body once they have been cooked.

1. The watermelon is a kind of _____.     

A. drink      

B. fruit      

C. medicine      

D. vitamin

2. How does a scientist usually test a theory?   

A. By practicing it in daily life.  

B. By doing scientific research.

C. By discussing it with other scientists.

D. By looking into many scientific reports.  

3. Lycopene is something that gives tomatoes and watermelon their ____ color.     

A. red        

B. green      

C. black        

D. yellow

4. To make full use of tomatoes, we'd better _______.

A. eat them raw              

B. not peel them

C. cook them first            

D. make them into juice  

5. Which of the following is TRUE according to the passage?   

A. Our bodies cannot absorb lycopene.

B. Watermelon is good for us in hot summer.  

C. Tomatoes have more lycopene than watermelon does.  

D. Lycopene in watermelon is hard for our bodies to absorb.

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傣族有哪些民间舞蹈形式

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通过以下哪些途径不能增强糖皮质激素的抗炎作用()

A.去掉10位的角甲基

B.C-6位上引入甲基

C.C-9位上引入氟原子

D.C-16位上引入甲基或羟基

E.C-1位上引入双键

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淘米水的肥力、去污力温和,可用来洗菜、浇花或洗碗。不仅(),而且不污染水质。

A.节约用水

B.节省洗涤剂

C.节约时间

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