Dear professor Yu,
I am writing this letter to present my sincere gratitude for all the credit and help you have given me during your teaching of the American literature.
Upon first entering your class, I had little knowledge on American literature. It was your profound knowledge that led me on the road of literature. Since then, I found myself attracted to it. In addition, I was pretty encouraged by your teaching style. Your description of various kinds of essays and novels was so vivid that I was always immersed in it, which was why I achieved much in your class. Besides, your sense of humor added plenty of fun to our class.
With all the great lectures you have given, I developed a deep love of American literature. Therefore, I would like to thank you again for your incomparable enlightenment on my academic career.