差速离心法的缺点有（） A.沉降系数在同一个数量级内各种粒子不易分开 B.壁效应严重

阅读理解。

     One day a farmer went out for a walk with his little son. The farmer wore a pair of wrong shoes. One

had thick sole (厚鞋底) but the other didn't. He began to walk and then his feet hurt. When he was just out

of the house, he turned to his son and said, "Why is one of my legs longer than the other today?"

     The son looked at his father's legs carefully as he was walking and then laughed, "Oh, no, Daddy. Your

legs are all right. You're wearing the wrong shoes." The farmer was very happy to hear that and said to

himself, "What a clever son!" Then he asked his son to go back and got the other pair of shoes for him.

The farmer had only two pairs of shoes.

     When the son ran back to the house, he found that the other pair was also a wrong pair. He had to return

to his father with nothing in his hands and said, "It's no use changing them, Daddy! The shoes at home are

not a pair, either!"

根据短文内容，完成下列各题。

1. One day a farmer wore _________ to walk with his son.

2. Was one of his legs longer than the other?

    ______________________________________________________________________

3.                 found the farmer's legs were all right.

4. The son came back to his father with                 .

5. Is the son really clever or not?

    ______________________________________________________________________

施工现场的通风、照明、安全卫生、防护设施是属于施工环境中的（）环境的内容。

A．劳动作业

B．自然

C．社会

D．地理

“实施城镇化战略，促进城乡共进步”的基本策略是党中央在哪个文件中明确提出的( )

A．2000年全国人大通过的《国民经济和社会发展第十个五年计划纲要》
B．2000年6月，中 * * 、国务院发布了《关于促进小城镇健康发展的若干意见》
C．2002年8月2日，国务院九部委联合发出《关于贯彻落实<国务院关于加强城乡规划监督管理的通知>的通知》
D．2006年年初，《中 * * 国务院关于推进社会主义新农村建设的若干意见》

高度危险性物品

预制电联结线时，底圈距线头间留有一定的调整余量，一般为（）。

A、200～300mm

B、300～400mm

C、400～500mm

D、500～600mm