1. 阅读下面短文，按照句子结构的语法性和上下文连贯的要求，选择可以填在横线上的最佳选项。

As we know, trees are of great importance to us. They not only produce oxygen for us to breathe,1also provide us with rich materials(材料). Many things in our daily lives come from trees. For example, lots of the furniture is made2wood. Besides, there are many3things you use almost every day, such as pencils, paper and so on. Trees are so important that it's everyone's duty to protect4.

However, people cut down plenty of trees5money every year. As a result, trees are in  6now. Luckily, there7still a lot of things all of us can do! We can plant more trees. It is  8easy way to help protect the environment. Ask your parents if you can plant some trees in your backyard or ask your teacher if you can plant trees in the school. Additionally, knowing about the forest problems is very important, too. Discuss them with your classmates. And you can even tell your parents what you learnt.

We can't imagine9in a treeless world. Without trees, it would get too hot for us to live on the Earth. So, to have a good living environment, we must10good care of trees and stop cutting them down.