问题
单项选择题
变频器如果采用电位器控制频率时，电位器阻值应选用（）Ω。
A.100
B.1000
C.10
D.50
答案
参考答案：B
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变频器如果采用电位器控制频率时，电位器阻值应选用（）Ω。
A.100
B.1000
C.10
D.50
参考答案：B
In Britain, people have different attitudes(态度)to the police. Most people generally 1 them and the job they do, but some people said that the police shouldn’t have special 2 . What does a policeman actually do? It is not a(n) 3 job to describe. After all，a policeman has a number of jobs to do. A policeman often has to 4 traffic, either on foot in the centre of a town, or in a police car on the roads. Indeed，in Britain, he might be in the Traffic Police and spend a lot of time 5 up and down main roads. A traffic policeman has to help keep the traffic moving，stop speeding cars and help when there is a(n) 6 . A policeman has to help keep the 7 ，too. If there is a fight, we 8 the police to come immediately. And they often have to deal with situation at great risk of their own 9 . We want the police to solve crimes，of course，so an ordinary(普通) policeman, 10 he is not a detective，he will often have to help 11 criminals. And 12 do we call when there is an emergency—an air crash，a fire or an earthquake？Of course the police. So a policeman has to 13 to face any terrible emergency that may happen in the modern world. The police do a 14 job，they do it so well that I support them. But I do not envy policemen. I do not think that I could 15 do the job of a policeman.
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