变频调速是通过改变电机定子绕组供电的()。来达到调速的目的。
A. 频率
B. 转速
C. 磁极对数
D. 转差率
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在该公司裁减的员工中，那些虽然在找工作但是却没有找到新工作单位的人属于（）。
A. 劳动者
B. 失业者
C. 非劳动力
D. 就业者
Which of the following metaphors could the author most appropriately use to summarize his
A windmill.
B. A waterfall.
C. A treadmill.
D. A gyroscope.
E. A bellows.
It can be inferred from the passage that the author most probably thinks that giving the disenfranchised "a piece of the action "(line 46)is
A. a compassionate, if misdirected, legislative measure.
B. an example of Americans" resistance to profound social change.
C. an innovative program for genuine social reform.
D. a monument to the efforts of industrial reformers.
E. a surprisingly "Old World" remedy for social ills.
Which of the following statements would provide the most of logical continuation of the final paragraph of the passage？
A. Thus Wynne — Edwards" theory raises serious questions about the constancy of animal population in a region.
Because Wynne- Edwards" theory is able to explain more kinds of animal behavior. than is the density-dependent theory, epideictic explanations of population regulation are now widely accepted.
C. The results of one study, for instance, have suggested that group vocalizing is more often used to defend territory than to provide information about population density.
D. Some of these studies have, in fact, worked out a systematic and complex code of social behavior. that can regulate population size.
E. One study, for example, has demonstrated that birds are more likely to use winter-roosting aggregations than group vocalizing in order to provide information on population size.
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