阅读图文材料，完成下列要求。
    河流在弯曲段存在“凹岸侵蚀，凸岸堆积”的现象。
    法国罗纳河上的圣贝内泽桥始建于1177年，13世纪和15世纪曾大修和重建，1668年被废弃。1669年的大洪水冲毁了河流右岸的桥墩，后来左岸的残桥（图左侧图中粗实线）成为旅游景点——圣贝内泽断桥（图右照片）。

通过比较断桥处河流左右岸附近河水的深浅及流速差异，说明该断桥能保存至今的原因。

    Have you ever wondered what goes through your mind when you choose where to sit in a new classroom? Or in a waiting room full of strangers? Or on a bus? Researchers have found out some interesting facts.
    Perhaps unsurprisingly, we prefer to sit closer to people like ourselves. Girls sit by girls and boys sit by boys. Adults sit together and young people choose another young person to sit near. But it goes further than this. We even choose to sit near someone who looks like us. People with glasses are more likely to sit near other people with glasses. People with long hair sit closer to other people with long hair.
    We seem to believe that people with similar habits or hobbies will share similar attitude and we are more likely to be accepted by people like ourselves or even, we think we may be safer with people who look like us. Sometimes that’s true but it's a pity if we always stick to the same people, the same group. The danger in always staying in our comfort zone (舒适区) is that we just recycle the same opinions, the same tastes and the same ideas. We lose the chance to learn something new, find out about interesting things, hear funny stories and discover difference.

    When we always stick to the same people, how can we ever break down the barriers which prevent us from getting to know people with different ideas? And how can we avoid the ignorance (无知), which too often leads to prejudice (偏见) and even fear? If instead you wan t to live in a society that opens to changes and new things and different opinions, be the cat among the pigeons.
    Move out of your comfort zone. Go and sit next to someone different. And don't just sit there in silence. Say hello. Ask a question. Start a conversation. That’s how we make friends. That’s how we learn about people. That’s how we open our minds to new ideas. That's how we live an exciting life.

如图，是的直径，点为上一点，和过点的切线互相垂直，垂足为，交于点，直线交的延长线于点，连接，，．
求证：平分；
探究线段，之间的数量关系，并说明理由；
若，求的面积．

阅读下面语段，按要求答题。
    西沙群岛位于海南岛东南约180海里处，像一颗颗美丽的珍珠，镶嵌在碧波万顷的南海上。美丽的西沙，海水清澈幽蓝、晶yíng剔透；海面像一块巨大的深蓝色的绸缎随风摆动；海底是一个神秘世界，一丛丛、一簇簇的珊瑚像盛开的鲜花：金黄、雪白、鲜红…… ①________（A.五彩缤纷  B.五花八门）。最让你情不自jīn地浮想联翩，②________（A. 忘乎所以   B. 流连忘返）的是西沙日落的美景。傍晚，红彤彤的晚霞铺满半边天，海水鲜红闪亮，归巢鸟儿的鸣叫声和着轻轻拍岸的涛声传入耳中……
①给语段中加粗的字注音，或根据拼音写汉字。
镶嵌（  ）   ②清澈（  ）   ③晶 yíng（　）剔透  ④情不自jīn（　）    
②结合语境选择合适的成语，将字母序号填写在横线上。