简述土壤胶体的种类、化学特性及其对污染物迁移的影响。

Is there a magic cutoff period when offspring become accountable for their own actions? Is there a wonderful moment when parents can become spectators (旁观者) in the lives of their children and shrug, "It' s their life," and feel nothing?

When I was in my twenties, I stood in a hospital corridor waiting for doctors to put a few stitches in my son' s head. I was asked, "When do you stop worrying?" A nurse said, "When they get out of the accident stage." My mother just smiled faintly and said nothing.

When I was in my thirties, I sat on a little chair in a classroom and heard how one of my children talked incessantly, disrupted (打断) the class, and was headed for a career making license plates. As if to read my mind, a teacher said, "Don't worry. They all go through this stage, and then you can sit back, relax, and enjoy them." My mother listened and said nothing.

When I was in my forties, I spent a lifetime waiting for the phone to ring and the cars to come home, the front door to open.

My friends said that when my kids got married I could stop worrying and lead my own life. I wanted to believe that, but I was haunted by my mother' s wan ( 淡淡的 ) smile and her occasional words, "You look pale. Are you all right? Call me the minute you get home."

Can it be that parents are sentenced to a lifetime of worry? Is concern for one another handed down like a torch to blaze the trail of human frailties and the fears of the unknown? Is concern a curse? Or is it a virtue that elevates us to the highest form of life?

One of my children became quite irritable recently, saying to me, "Where were you? I' ve been calling for three days, and no one answered. I was worried! ! !"

I smiled a wan smile.

1.What can we know about the author’s mother from the passage?

A. She seems to laugh at the author.        

B. She is not concerned about the author.

C. She has a thorough understanding of the author.     

D. She tries to give the author some encouragement.

2.What did the author do in her forties?

A. She was less concerned about her children.          

B. She couldn't stop worrying about her children.

C. She would like her children to see her often.        

D. She became more patient with her children.

3.Why did the author smile a wan smile at the end of the passage?

A. She wanted to learn from her mother.                

B. She stopped worrying about her children at last.

C. She succeeded in tricking her children.              

D. She got a kind of satisfaction from her child's concern.

4.The main purpose of the passage is to tell us that ______.

A. the concern between parents and children is natural

B. parents’ love for their children is selfless

C. parents show more concern for their children        

D. parents will worry about their children all their lives

下列关于开普勒定律的说法正确的是（）。

A.开普勒定律认为每一个行星都沿各自的椭圆轨道环绕太阳，而太阳则处在椭圆中心

B.开普勒的定律给予亚里士多德派与托勒密派在天文学与物理学上极大的挑战

C.开普勒定律是对哥白尼日新宇宙体系的延续和扩展

D.开普勒定律与牛顿的万有引力定律和第二定律矛盾

燃烧器内二次风用途？

施工总承包方和分包方的项目管理都属于( )的项目管理。

A．投资方

B．施工方，

C．分包方

D．总承包方

经办人员收到客户的申请材料后，应按要求清点材料是否齐全，对材料的完整性、合法性、规范性、真实性和（）进行初步审查。

A、可比性

B、有效性

C、客观性

D、价值性