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问题 单项选择题

直流伺服电动机旋转时有大的冲击，其原因如：测速发电机在( )时，输出电压的纹波峰值大于2%。

A．550r/min

B．750r/min

C．1000r/min

D．1500r/min

答案

参考答案：C

单项选择题

航行中发现螺旋桨松弛，应立即采取的措施是（）。

A、抛锚

B、停车

C、把车速减至最低再停
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单项选择题

F: We ought not to test the safety of new drugs on sentient animals, such as dogs and rabbits. Our benefit means their pain, and they are equal to us in the capacity to feel pain.
G: We must carry out such tests; otherwise, we would irresponsibly sacrifice the human lives that could have been saved by the drugs.
Which of the following, if true, is the best objection that could be made from F’s point of view to counter G’s point

A．Even though it is not necessary for people to use cosmetics, cosmetics are also being tested on sentient animals.

B．Medical science already has at its disposal a great number of drugs and other treatments for serious illnesses.

C．It is not possible to obtain scientifically adequate results by testing drugs in the test tube, without making tests on living tissue.

D．Some of the drugs to be tested would save human beings from great pain.

E．(E) Many tests now performed on sentient animals can be performed equally well on fertilized chicken eggs that are at a very early stage of development.
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