题目

正三角形的外接圆及内切圆，它们是 ，正方形对角线的交点到 相等，所以正方形有外接圆，圆心就是 ，正方形对角线的交点到 相等，所以正方形有内切圆，外接圆与内切圆是 ． 答案：【1】同心圆 【2】各顶点距离 【3】对角线的交点 【4】各边距离 【5】同心圆先通读下面的短文，然后根据短文内容，在空格内填入一个最适当的词，所填单词必须在答卷标有题号的横线。每空只能填一字What is a hurricane?(飓风)You may already know that hurricanes are storms that can cause devastating(毁灭性的) waves, wind, and rain. They happen during “Hurricane Season,' from June 1st until November 30th in the Atlantic Ocean and from May 15th until November 30th in the Pacific Ocean.Categories(类别)of HurricanesThere are five categories of hurricanes, which are based on wind speeds. The categories help people know how much damage(危害) a hurricane may cause because the greater the wind speed, the more dangerous the storm. For example, a Category 5 hurricane has winds over 155 miles per hour, which are strong enough to break the buildings along the seaside completely.Hurricane DangersWhen a hurricane happens together with heavy rainfall（降雨）, there can be a devastating flood. The centre of a hurricane is called the eye. While most of a hurricane has dangerously strong winds, the eye in fact is a calm area in the storm. When the eye of a hurricane passes over land, people might think that it's over, but before long the wind and rain increase(增长) again as the second part of the hurricane moves through.Hurricane Safety TipsThere is no way to stop a hurricane or make it change direction, so if you ever find yourself in the path of a hurricane, be sure to stay inside during the storm. You could be seriously injured(受伤) if you go outside.HurricanesCharacteristicsDevastating waves, wind, and rain are usually the of hurricanes.CategoriesHurricanes are into five categories by scientists, based on wind speeds.The eye is the of a hurricane. Soon after it passes, the wind and rain increase again.Safety TipsIt's to stop a hurricane or change its direction..Stay inside during the storm, or you could be seriously injured.