荔枝、西瓜、水蜜桃都是人们喜爱的瓜果。

指出下面语段中使用的说明方法，并分析作用。

    我可以随便举个例子：一百年以前，世界的农业人口占人口总数的80%以上；今天，美国的农业人口，只占全国人口的1%到2%，可是他们生产出来的粮食，不仅可以供全美国人食用，还可以出口到世界各地去。

①说明方法： ____

②作用：____

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。