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问题 单项选择题

图示平面应力状态的σa，εa为（）。(已知α=45°，E、μ水分别材料的弹性模量和泊松比)

A.A

B.B

C.C

D.D

答案

参考答案：C

解析：

提示：(1)斜截面上的应力计算公式：

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选择题

—You ______ this new i—pad yesterday, right?

—No. I ______ it for a month. It works well, I think.

A．have had, had

B．bought, have bought

C．bought, have had

D．had, have bought
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单项选择题

Financial derivatives also provide a powerful tool for limiting risks that individuals and firms face in the ordinary conduct of their business. This is an example of:

A．

A. trading efficiency.

B．

B. speculation.

C．

C. risk management.
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