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【单选题】
人口抚养比是非劳动年龄人口数与劳动年龄人口数的比值。读我国五省市人口抚养比图，关于我国五省市人口抚养比，下列叙述正确的是 [ ]A.
贵州的少儿人口抚养比最大
B.
上海的老年人口抚养比最小
C.
北京的少儿人口抚养比大于广东
D.
江苏的少儿人口抚养比小于北京
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【简答题】三相异步电动机的电气制动方法有 、 和 三种。
【简答题】7)三相异步电动机的电气制动方法有 制动、 制动、 制动。
【单选题】While having orbited the sun, the satellite has sent more than four billion bits of information back to earth.
A.
orbiting
B.
to orbit
C.
being orbited
D.
having been orbited
【单选题】Who are more likely to inform. someone of their expected arrival time?
A.
Men.
B.
Women.
C.
Both men and women.
D.
Neither men nor women.
【简答题】For more _____________, please feel free to contact us. (inform)
【单选题】Which one is more formal?
A.
This is to inform. you that your book has been rejected by our publishing company as it was not up to the required standard. In case you would like us to reconsider it, we would suggest that you go over it and make some necessary changes.
B.
You know that book I wrote? Well, the publishing company rejected it. They thought it was awful. But hey, I did the best I could, and I think it was great. I?m not gonna redo it the way they said I should.
【简答题】在新农村建设中，为将一批建材运到10 m高的施工处，工人利用如图所示的滑轮组提升建材。装置中动滑轮重100N，工人每次匀速提升一箱重400N的建材，不计绳重和摩擦。试问： (1)每次提升建材时的有用功、额外功各是多少？ (2)该滑轮组的机械效率是多少？ (3)为加快施工进度，张师傅建议用电动机做动力替代人提升建材。为了安全，改装后每次可吊起四箱建材，建材匀速上升时的速度为0.4m/s。仓库中现有两...
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