选择题：轴向拉伸（压缩）时，在杆件的横截面上，正应力为________值；在与杆件轴线方向 45°的斜截面上

题目内容：

轴向拉伸（压缩）时，在杆件的横截面上，正应力为________值；在与杆件轴线方向 45°的斜截面上，剪应力为 _______值。

A.最大
B.最小
C.不能确定
D.为零

参考答案：

[填空题,5分] They have been receiving a four-day _____

[填空题,5分] They have been receiving a four-day ______(intense) training course.

设随机变量(X1,X2)具有概率密度。f(x,y)=(x+y),0≤x≤2,0≤y≤2求X D ( X 1 + X 2 ) ( X ) ) , E ( X 2

[填空题,5分] He left in such a big hurry that he forget()(take) the documents with h

[填空题,5分] Eight hours’ sleep is the _________(最低限) that children should have.

[填空题,2.4分] The man who has _ _（决定、下定决心）to win will never say “impossible.”