[解析]
Dear Tom,
Thank you very much for your invitation.
I'd like to accept it and take this opportunity to introduce the traditional Chinese painting to foreign friends,but I'm sorry to inform you that I can't.The reason is that I am busy preparing myself for the coming final examination.【谢绝邀请及原因】
I strongly recommend my friend Mary,who is the most suitable choice to take my place next week.(高分句型一) She began to learn painting at an early age and has a good knowledge of the traditional Chinese painting,which,together with her active personality and perfect spoken English,will help make your activity a success.(高分句型二)【推荐Mary】
Sorry again for any inconvenience caused by my absence.
Best wishes.
Yours sincerely,
Li Hua