齿轮泵依靠（）过程中工作容积变化来输送液体。
A、叶轮高速旋转
B、齿轮相互啮合
C、高速旋转齿轮
D、柱塞运动
参考答案：B
Yesterday evening, I went to the train station to see my best friend _____. [ ]
A. off
B. up
C. through
D. out
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