【正确答案】 Dear Mrs. Liu,
I' m writing to you to say goodbye to you. I' m going to return to Canada tomorrow morning. Before I return to Canada, I want to express my thanks to you. I am very glad to work together with you in the past year. I am grateful for all you have done for me both in teaching and in life. Besides, I really enjoy teaching in this school. I have spent a good time here. I will never forget the lovely students. I love China and all the friends here. I will certainly miss you when I am back to Canada. Probably I will come back some day. By the way, I leave some English books to your library and I hope they will be useful to your students.
Yours truly,
Helen