某城市100户居民的月平均用电量(单位:度),以160,180),180,200),200,220),220,240),240,260),260,280),280,300分组的频率分布直方图如图所示.

若两个相似多边形的面积之比为1：4，则它们的周长之比为（　　）

2009年5月，世界卫生组织召开成员国会议研究防控甲型HIN1流感的对策。中国政府表示，在做好国内疫情防控的同时，将加强与世界卫生组织、有关国家和地区的交流与合作，并提供必要的防控物资、经费和技术支持。这表明              
①解决国际问题必须通过国际组织          
②国际组织是国际合作的纽带
③中国在国际事务中发挥主导作用          
④中国在国际事务中发挥建设性作用

阅读短信，选择方框所提供的单词使信的内容完整、正确。

think, say about, I, sale, woman, for, health, don't, old

Dear Jane,

    Thank you ____ your letter. I am fine. And how are you? I am 12 years ____. I am happy today because it's March 8th, it's ____ Day. I want to buy a pair of trousers for ____mother. She is busy every day, and I want ____ “Thank you” to my mother, too. Mr. Hot Clothes Store is near my home. Many clothes are on ____. They have green trousers for only $20. My mother likes green, but my father ____. He ____blue looks nice. Do you like sports? I like playing sports, I want to be ____.

What ____ you? I want to know you and be your friend.

Tommy

The managing director took the _____ for the accident, although it was not really his fault.