Yesterday was Sunday. I went to the park with my classmates. There we had a picnic and played happily. Then, we decided to go home. On our way home Fangfang suddenly said she left something there and we had to go back to the park. When we arrived there, we found nothing but the rubbish we left. Then we understood why she asked us to come back. We all began to pick it up. Although it took us about twenty minutes to pick up all the rubbish, we felt very happy. Taking care of the environment is our duty. We should not throw rubbish about.