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问题 单项选择题

按转子磁场定向和矢量控制变频调速系统中，在（）条件下，有电动机转矩与定子电流转矩分量成正比的关系。

A．气隙磁通恒定

B．转子电流恒定

C．转子磁链恒定

D．定子电流恒定滞后60°

答案

参考答案：A

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阅读理解。
                                                  Trip 1  One Week in The Mountains
Bring your strong shoes and warm clothes for this walk in a beautiful area of the Green Mountains. You
may go hiking or have a try of rock climbing. This is also a protection area for wild animals. You can find
many kinds of animals living in this area.
Time: May 8-May 14            
Tel: 64639818
Adult (成年人): $1l0.00           Child: $55.00
                                       Trip 2  Three Days In The Country
There are many beautiful gardens. Take your camera and enjoy the wonderful sight in Hunter Valley. It
is a good place for fishing and horse riding. You can also find different kinds of flowers here. This is also
a great walk for bird-lovers.
Time: May 20-May 22      
Tel: 63986432
Adult $55:00                Child: $25.00
                                               Trip 3  Flashlight Adventure
Put on your warm cloches, bring a flashlight (手电筒) and come for a night walk along the Dungog
Valley. It is a trip full of adventure (冒险). A guide will lead the tour. Many of the plants you will see
on this trip can only be seen at night.
Time: May 16-May 18    
Tel: 63875629
Adult: $30.00              Not for children
                                            Trip 4  Five Days By The Sea
Wear your sun hat and enjoy wonderful sunshine all the time from morning to evening. Our hotel is next
to the sea. We have our own boats too. You can swim in the sea or in the swimming pool. Every day
our boat will take you to different places for swimming.
Time: May 23-May 27      
Tel: 67538293
Adult: $80.00               Child: $40.00
 
1. What number may you call if you and your friends want to enjoy the sunshine at the seaside?
A. 67538293.
B. 63986432.   
C. 64639818.
D. 63875629.
2. Sam wants to stay in Hunter Valley with his wife, his five-year-old daughter and his seven-year-old son. How much will 'it cost?
A.$25.
B.$50.
C. $l00.
D.$150.
3. David loves sports. He will take his holiday from May 7 to May 15. What activity will he probably take
part in?
A. Hiking in the mountains.
B. Fishing in the country.
C. Watching plants at night.
D. Swimming in the sea.
4. Lucy is a college student. She is quite interested in science. She wants to know something about the life
of plants at night. Which trip will she choose?
A. Trip 1.
B. Trip 2.
C. Trip 3.
D. Trip 4.
5. Which of the following is NOT mentioned according to the four advertisements?

    A        B        C      D
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单项选择题

高危妊娠定义为（）

A.有危害胎儿的妊娠

B.对母体有危害的妊娠

C.有导致难产的妊娠

D.可导致母体死亡的妊娠

E.凡危害母儿或导致难产的妊娠
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