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问题 单项选择题

船舶电力推进系统的推进装置类型有哪些？（）

A.可变螺距式推进器和轴系推进装置两种

B.旋转式推进器和轴系推进装置两种

C.吊舱式推进器和轴系推进装置两种

D.吊舱式推进器和悬挂式推进装置两种

答案

参考答案：C

单项选择题

Which of the following statements is true of the Parkinson’s disease
a. Parkinson’s always shows the same symptoms on different people.
b. People inflicted with Parkinson’s often have a shaking hand or a stiff hand.
c. The symptoms of Parkinson’s vary among different patients.
d. Victims of Parkinson’s find it difficult to recall what they have eaten for dinner.
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问答题 简答题

失访偏倚是队列研究难以避免的一种偏倚，特别是较大型及较长时间的研究。为了将失访偏倚的影响减到最低，应当采取哪些措施？
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