关于应力圆的下列说法，只有（）是正确的。 A.对于单向应力状态_爱下问搜题

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问题单项选择题

关于应力圆的下列说法，只有（）是正确的。

A.对于单向应力状态，只能作出个应力圆；对于二向应力状态，在两个主应力相等时，只能作出一个应力圆，其他情形能作出三个应力圆；对于三向应力状态，三个主应力相等时，只能作出一点圆，两个主应力相等时，只能作出一个应力圆，其他情形，可作出三个应力圆

B.单向应力状态只能作出一个应力圆，其他应力状态能作出三个应力圆

C.二向应力状态与单向应力状态一样只能作出一个应力圆

D.三向应力状态都能作出三个应力圆

答案

参考答案：A

选择题

抛物线y=（x+2）²-1可以由抛物线y=x²平移得到，下列平移方法中正确的是（　　）

A．先向左平移2个单位，再向上平移1个单位

B．先向左平移2个单位，再向下平移1个单位

C．先向右平移2个单位，再向上平移1个单位

D．先向右平移2个单位，再向下平移1个单位

填空题

用所给单词的适当形式完成句子。

1. The water in our city is _ __ (recycle) many times.

2. A new bridge is being ___ (build) in the river.

3. These boys are __ (pull) their boat out of the lake.

4. Many _ (roof) were blown away by the strong wind.

5. We can see a lot of _ _ (can) on the ground in the park.

6. The old school _ (pull) down and a new one is being built.

7. My sister joined a university film _ (social).

8. Some students (dance) while others were singing.

9. You should stop (worry) about it.

10. Our new school is the ____.