作文主题的“环保活动”（根据材料要求，是参加过的活动，所以宜用一般过去时）而不是“环保的重要性”。Protecting the environment is everyones duty. As we know, the environment around us is getting worse and worse. So I think we must do something to protect the environment.So I took part in an activity to protect environment last week. About five hundred people took part in the activity. Firstly, we decided to go to school or go to work on foot every day. It is good for our environment.Then, we went to our city park. We helped clean the city park. Because our city park is dirty. It has a lot of rubbish. We helped clean up the park road and the park lawn.Lastly, we went to the hill to plant trees and flowers. Because trees can provide us with oxygen make the air around us fresh. And trees make our environment more beautiful. Trees are very important to us. We have planted about one thousand trees.Its important for us to protect the environment.Protecting the environment is everyones duty.Last month, I went to plant trees with my friends. We got there by bike, then we began to plant trees. It was very hard to plant a tree, but we didnt give up. At first, we dug a hole. Then, we put a tree into it. Finally, we covered the soil and watered the trees.At about 4:00 in the afternoon, we finished it, then ,we came back.We were very happy.Protecting the environment is everyones duty.Last year, I took part in an activity with other people. In order to make my neighborhood more cleaner, my friends and I took part in it.We did many things. We picked up the rubbish around my neighborhood. And then, everywhere was clean and tidy. We also told the younger kids not to throw the rubbish anywhere. And we told some people that they should go to work by bike or by bus, not by car. We told everyone that its important for everyone to save water. At last, more and more people joined us. Now, my neighborhood is much cleaner than before.If everyone try his best to protect the environment. We will have a bright future.