问题 单项选择题

下列关于变压器的叙述中错误的是( )。

A.变压器只能改变交流电的电压,不能改变直流电的电压
B.变压器空载的效率等于0
C.变压器满载的效率等于1
D.变压器的额定电流是指变压器在额定容量下,允许长期通过的电流

答案

参考答案:C

阅读理解

阅读理解。

     A young man once went into town and bought himself a pair of trousers. When he got home, he went

upstairs to his bedroom and put them on. He found that they were about two inches too long. He went

downstairs to the kitchen. His mother and two sisters were washing up the tea-things there. "The new

trousers are too long," he said politly. "They need shonening by about two inches. Could one of you do

it for me, please?" His mother and sister were busy and none of them said anything. But as soon as his

mother had finished wash'ing up,she went quietly upstairs to her son's bedroom and shonened the

tmusers by two inches. She came downstairs without saving anything to her daughters.

     Later on. after supper, the elder sister remembered her brother's trousers. She was a kind-hearted

girl, so she went quickedy upstairs without saying anything to anyone,and shortened the trousers by two

inches.

     The younger sister went to the cinema, but when she came home,she also remembered her brother's

trousers. So she ran upstalrs and did as her mother and sister had done. You can imagine the look on the

young man's face when he put the trousers on the next morning.

1. The young man's trousers were _____ for him at first.

A. a bit too long    

B. very good    

C. not too long    

D. too shon

2. The young man's mother and sisters didn't answer because they were busy _____ in the kitchen.

A. cooking        

B. making tea

C. washing clotlles    

D. washing cups,glasses and so on

3. His elder sister shortened the trousers _____.

A. in the evening    

B. after lunch

C. as soon as she had finished the  washing    

D. after she came back from the cinema

4. The next moming the young man found that the trousers were _____ inches too short for him.

A. two    

B. four    

C. six    

D. eight

5. We can imagine that when the young man put the trousers on the next morning, he Would feel _____

A. happy    

B. surprising    

C. surprised    

D. thankful

单项选择题