一元二次方程（x﹣1）²=0的解为（　　）

①以原点 $O$ 为对称中心，画出与 $△ABC$ 关于原点 $O$ 对称的 $△A_1{B}_1{C}_1$ ．

②将 $△ABC$ 绕点 $O$ 沿逆时针方向旋转 $90°$ 得到 $△A_2{B}_2{C}_2$ ，画出 $△A_2{B}_2{C}_2$ ，并求出 $A{A}_2$ 的长．

，          。古今有识之士治学都很注重“博观而约取”。观而有选，取而有择，有的放矢。韩愈在《原道》中批评有些人读书作文“择焉而不精，语焉而不详”。袁枚在解释杜甫诗句“读书破万卷，下笔如有神”时说：“盖破其卷，取其神，非囫囵用其糟粕也。”爱因斯坦则说：“在书本中找出可以把自己引到深处的东西，把其他一切统统抛掉，抛掉使头脑负担过重并将自己诱离要点的一切。”这些真知灼见，发人深思。

    Different countries and people have different manners(举止).Here are some examples:If you visit a Chinese family,you should knock at the door first.When the door opens,you should not move before the host says “Come in,please.” Before coming into the house in Japan,it is good manners to take off your shoes.In European(欧洲的) countries,even if your shoes are very dirty,it is not necessary to take them off.In England,a guest(客人) always finishes the drink or the food to show that he enjoys it.This will make the host very pleased.

根据短文内容完成信息表，每空一词。

用天平测物体质量：