如图所示的电路中，R₁、R₂均为定值电阻，且R₁=100Ω，R₂的阻值未知，R₃是一个滑动变阻器，在其滑片从最左端滑至最右端的过程中，测得电源的路端电压U随电流I的变化图线如图所示，其中图线上的A、B两点是滑片在变阻器两个不同的端点时分别得到的．求：

A,B,C,D是四种粒子的结构示意图．

2010年6月至7月初，世界杯足球赛将在南非举行．读图，回答下列问题

刘泽华（中国古代政治制度研究专家）在某著作的序言中写道：“在这种政权结构中，各级大大小小的封建官僚，就是这部大机器上的无数小螺丝钉；而最高的君主，便是这部巨大机器的总操纵者。……官僚们永远只能是君主的工具，官僚机构只能是君主的办事机构。”对上述表述理解不正确的是（    ）

    Everyone needs friends. Friends bring us happiness and hope in our lives. But the ability to make friends changes from person to person. To some people, making friends is easy, and to others it's very difficult.
    Making friends is a skill, and the first thing is to know how to get on with others. If you have trouble in making friends, maybe I can tell you how to do it.
    Realize your own good points. You have skills and talents(才能) that others will like.
    Believe that you are a good person and have something nice to share with others.
    Be humourous. Learn to laugh at yourself and your weakness. Remember to smile at others.
    Respect(尊敬) the others. Everyone has his own idea. Learn how to listen to others; ideas without trying to make them accept(接受) yours.
    Be kind. If you are kind to others, they will usually be kind to you. There are hundreds of little things you can do to show your kindness. Open the door for someone. Wave to a friend and so on.
    Don't complain(抱怨). Learn to accept what you can't change, and work hard to change what you can. No one is willing to hear your complaints all the time.
    Never give up. Even if you are faced with some closed-minded people, never give up. And try to find someone who will understand you.