【答案解析】

Dear Professor Robinson,
I take great pleasure in recommending Zhang Lin, one of my favorite students, for admission into your distinguished graduate program. As her tutor, I found her a diligent student with research potential in chemistry.
Her performance in chemistry is outstanding. First, she had shown great talents in participating in the national chemistry competition and ranked the ninth. Second, she was born with a keen mind for science research. In my experience with her, I was impressed with not only her extraordinary intelligence but also her persistence. She has the patience to stay in the lab and do experiments all day long. In addition, she is a careful and considerate person and you can rest assured when working with her.
I hereby recommend her to you with all my heart. Your favorable consideration to this letter will be most appreciated. I am sure that she will be an outstanding student in your graduate program. Looking forward to hearing from you.