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【简答题】
16 一带传动,紧边拉力F1与拉力F2之比<10。当空载时,它们的比值为 ;当载荷小于值时,它们的比值为 ;当载荷达到刚开始打滑的瞬间,它们的比值为 。 a)F 1 /F 2 ≈1 b)F 1 /F 2 ≈0 c) F 1 /F 2 =e μα d)F 1 /F 2
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反馈参考答案：
举一反三
【单选题】He _____ articles for our wall-newspaper these three years, and he _____ about forty articles.
A.
has been writing； has written
B.
has been writing； wrote
C.
is writing； has been writing
D.
has written； has written
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