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问题 单项选择题

往复式氢气压缩机盘车是为了使（）位于中间位置，同时检查各转动部位是否紧固、转动是否灵活。

A、十字头

B、活塞

C、气阀

D、平衡块

答案

参考答案：B

单项选择题

Questions 27～30

A. Their lecturer-student ratio is not reasonable.
B. Their staff is not interested in helping students.
C. Their lecture halls are not well equipped.
D. Their degrees are not accepted by employers.
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单项选择题

快速射血期（）。

A．房内压＞室内压室内压＞动脉压

D．房内压动脉压

E．房内压＞动脉压＜室内压
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