到三角形三个顶点距离相等的是（　　）

(材料分析题)阅读下面的图文资料，并回答问题。

材料一：l519年9月，航海家麦哲伦率领一支200多人的探险船队，分乘5艘帆船从西班牙出发，向西南穿越大西洋，绕过南美大陆南端的海峡，进入太平洋。一路上船员们历尽了千辛万苦，还有不少人病死在途中。

1521年3月，船队到达菲律宾群岛，麦哲伦因介入岛上部族纠纷，被当地居民杀死。最后，船队只剩下1艘帆船和l0多名船员。他们向西穿过印度洋，绕过非洲南端的好望角，终于在1522年9月回到原出发地酉班牙。麦哲伦船队首次完成了环绕地球一周的航行。

材料二：麦哲伦船队环球航行路线图(图3—1—7)。

（1）麦哲伦坚信大地是____ 形的，从地球上的一点出发，一直朝一个方向走，一定能重新回到出发点。
（2）三年的环球航行中，麦哲伦船队先后经过的大洋是____ 洋、____ 洋、____ 洋，最后又回到了最早出发的____ 洋。
（3）你能够从人类认识地球形状的艰难历程中感悟到什么?____ 。

阅读短文，下列问题

    People in many countries are learning English.Some of them are small children. Others are teenagers. Many are adults. Some learn at school, others learn by themselves. A few people learn English by hearing the language over the radio, on TV or in films. As we know, it's hard to learn a foreign language well. One must work hard to learn another language. Because we can't use it often. But if you have right ways to learn English, it's a piece of cake.

    Why do all these people want to learn English?It is difficult to answer this question. Many boys and girls learn English at school because it is one of their subjects required (要求) for study. They study their own language, math and English. Some people learn it because it is useful for their work. Many people learn English for their higher studies,because at colleges or universities some of their books are in English. Some people learn English because they want to read newspapers or magazines in English.

根据短文内容选择正确答案。