For a moment, I even thought that this was some sort of test, and that this woman was someone from the head office, testing my loyalty. 一刻, 我甚至认为这是某种考验, 。
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参考答案:
举一反三
【简答题】如果r为螺杆的根半径、R为螺杆的顶半径、a为两螺杆中心距。
则( )为全啮合式双螺杆A. a=R+r B. R+r<a<2R C. a<R+r D. a>2R