问题 选择题

三角形的外心具有的性质是(   )

A.到三边的距离相等

B.到三个顶点的距离相等

C.外心在三角形外

D.外心在三角形内

答案

B.

题目分析:根据三角形外心的定义进行解答即可.

A、∵三角形的外心是三角形三条边垂直平分线的交点,∴到三边的距离相等不一定相等,故本选项错误;

B、∵三角形的外心是三角形三条边垂直平分线的交点,∴到三个顶点的距离相等相等,故本选项正确;

C、∵锐角三角形的外心在三角形的内部,∴外心不一定在三角形外,故本选项错误;

D、∵顿角三角形的外心在三角形的外部,∴外心不一定在三角形内,故本选项错误.

故选B.

考点: 三角形的外接圆与外心.

阅读理解

阅读短文,选择正确选项。

       In the United States, every year, Thanksgiving Day is on the fourth Thursday of November. Because

Canada is north of the United States, and is colder. The harvest comes earlier in the year. In Canada, people have

Thanksgiving Day on the second Monday in October. 

       The harvest brings a lot of food to the people. On Thanksgiving Day people in Canada and America like to

have a big meal with their friends and family just like Chinese people do at Mid-Autumn Festival. Many

Canadians and Americans put flowers, vegetables and fruits around their homes to say "Thank you" for the

harvest.

       At a Thanksgiving Day dinner, many Canadians and Americans will eat turkey, potatoes, and pumpkins pie.

These are food like the food of many years ago. They are saying "Thank you" for the harvest that comes every

year.

1. Which country has the Thanksgiving Day like the United States? [ ]

A. Japan.

B. China.

C. Canada.

D. Korea.

2. In the United States, Thanksgiving is on the fourth Thursday of            . [ ]

A. January

B. May

C. November

D. December

3. Canada has Thanksgiving earlier in the year because             .[ ]

A. they like flowers

B. the harvest come earlier

C. they have a big meal

D. they want to be different

4. The harvest brings               to people.[ ]

A. flowers

B. turkeys

C. food

D. pumpkins

5. What do people usually say on Thanksgiving Day for the harvest? [ ]

A. Good morning.

B. I'm hungry.

C. Hello.

D. Thank you.

单项选择题