假设你是李华，交换生Tracy刚刚结束在你们学校的学习生活，已经返回英国。作为班长，请你根据以下内容用英语写一分感谢信，感谢她一学期以来带给大家的美好回忆： 1. 怀念与她相处的快乐时光； 2. 感谢她对大家英语学习的帮助； 3. 感谢她为班级捐赠的英文书籍； 4. 欢迎她有机会再来中国。

One possible version Dear teachers and friends, I'd like to say something before Tracy goes back to England. Tracy is a very kind and friendly girl and I feel happy to be her friend. She gets along well with everyone and all of us have a wonderful time with her. Whenever we have trouble learning English, she doesn't hesitate to help us and our English has been improved a lot since she came to our class. We owe a lot of thanks to Tracy. True friendship never ends, so I hope we can keep in touch with Tracy. I also hope that Tracy can come back to China and stay with us in the near future. That's all. Thank you.