为在池塘两侧的A，B两处架桥，要想测量A，B两点的距离，如图所示，找一处看得见A，B的点P，连接AP并延长到D，使PA=PD，连接BP并延长到C，使．测得CD=35m，就确定了AB也是35m，说明其中的理由；

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Dear Amy

    It is very exciting that you are coming to our school so soon. Before you arrive, let me introduce our school to you.

    Our school is quite famous for____(it) long history. It was begun in the early 1920s. It is a good place for us____prepare) ourselves for the future. We have many wonderful teachers____are always ready to offer help. They encourage us to try out new ideas and ask questions.____their help we have developed all kinds of interests in both arts and science. Students can choose to join any school clubs they are____(interest)in. We can also choose the subjects____we want to study. Last term I selected American Literature____I wanted to learn about famous American writers. This term I____(choose)to attend music classes because my father bought me a piano as a birthday present.

    I love my school and hope____you will have a pleasant experience here too. I am looking forward to____(meet) you soon!

Yours

Lily