根据短文理解，从A、B、C、D四个选项中选择最佳一个答案填空。
Leigong Mountain is well-known for its plants and animals. Every year, 1 from all over the country and even abroad come to visit it. It has become one of the most popular sights in Qiandongnan. Visitors 2 us a lot of businesses, jobs and money. If it's 3, visitors can see many kinds of 4 in the tree singing and some rare animals like monkeys climbing up and 5.
Last Saturday, several of my friends and I went there 6. After about one-hour ride, we arrived there. To our 7, some visitors didn't pay attention to protecting the environment. Plastic bags and bottles were thrown 8. We had to 9 the rubbish and put it into the dustbin. I think we should protect Leigong Mountain from being 10, or the pollution will keep the visitors away. Let's take action to make LeiGong Mountain more and more beautiful.
