直径为d的圆截面钢材受轴向拉力作用已知其中纵线应变为ε,弹性模量为E, 则杆的 轴力为_______

直径为d的圆截面钢材受轴向拉力作用已知其中纵线应变为ε,弹性模量为E, 则杆的 轴力为___________ A.πd2ε/4E B.πd2E/4ε C.

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设X1,X2,…,X6是来自N(u,02)的样本,S2为其样本方差,则DS2的值为( A)1/3 o

设X1,X2,…,X6是来自N(u,02)的样本,S2为其样本方差,则DS2的值为( A)1/3 o 4. : ( B ) 1/5fo . : ( C)2/5

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- I was worried about my driving test, but I passe

- I was worried about my driving test, but I passed it.- ____________________选择一

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He____________ to Shanghai for I saw him a minute

He____________ to Shanghai for I saw him a minute ago. 选择一项:A. can’t goB. can’t

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