材料一：
   
材料二：“山地之国”瑞士多样的地形，奇特的景观使其成为旅游胜地，夏季众多的山峰吸引着大批登山爱好者，冬季滑雪爱好者云集，旅游业成为瑞士的支柱产业之一。人们对生态环境厚爱有加，修建了阿尔卑斯山区的自然保护区，为濒危动物提供了安全的生存地。

任务型阅读   

My name is Scott．I am an American boy．I am thirteen years old，Now I am a student in Great School in Dalian，Liaoning．I am in Class One，Grade Seven．I like sports．My favourite sport is table tennis．But I can 't swim．My mother is a music teacher．

She can sing and dance．can the，play，she，piano(?)Yes，she can．My father is a hotel manager．He can speak Chinese，English，Japanese and Russian．He is popular in the hotel．

根据短文内容，完成下列各题。   

1﹣$\frac{1}{2}$﹣$\frac{1}{20}$﹣$\frac{1}{200}$﹣…﹣$\frac{1}{2000000000}$．

决定元素种类的是  (       )