阅读理解

    What's your hobby? Reading，playing sports or going to the movies?Hassan has an interesting hobby．He likes collecting tropicalfish(收集热带鱼)! He keeps this hobby for 7 years．Now he is 14．There is a big aquarium(养鱼缸)in his room．It is from his parents for his 13th birthday．There are many fish in it．All of the fish are cute and beautiful．

    Hassan often travels around the world(周游世界)with his family．He loves it because he can see the underwater world in many places．He always loves the colorful underwater world．Under the water,he can see lots of tropical fish．Sometimes he can see sharks(鲨鱼)．He wants to keep one or two small sharks in an aquarium,but he can't do it at home．So Hassan goes to help in the zoo on the weekend．There he can see a lot of sharks and some other big fish．Hassan likes working in the zoo，because he can work with his favorite animals and leam more about them．

根据材料内容选择最佳答案。

田纳西河干流上的水库开始放水的时间是(    )

如图，弧AD是以等边三角形ABC一边AB为半径的四分之一圆周，P为弧AD上任意一点，若AC=5，则四边形ACBP周长的最大值是（　　）

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把盛有水的纸盒放在火焰上烧，水烧开了纸盒仍不会烧着，这是因为（　　）