题目内容：

根据短文内容和所给中文提示写出单词的正确形式，每空限填一词。

With the development of economy, traveling has become part of our lives. Every year ____1.___ （几千）of tourists choose to travel ___2.__（国外）to enjoy the beautiful scenery. But a few years ago, a lot of bad __3.___（行为）happened quite often during the travel. Some__4.____（扔） litter, painted on the walls, and spat on the ground everywhere. Some picked flowers, ___5.____（毁坏）trees and hurt animals. And even____6.____（更槽糕）, some smoked in the woods. How dangerous!

Luckily, things have _7.___（改变）now. Rubbish is always put into dustbins. People are friendly to animals. Nobody is __8.____（允许） to smoke around the woods and places of interest are well kept. All these changes make us __9.___（高兴）.

As a student, I think we should know it’s our duty to protect the___10._____（环境）. In order to make the world more beautiful, let’s behave well .