【正确答案】 Dear Xu Peng,
I' m writing to express my apology to you. I am very sorry to tell you that I won' t be able to attend your birthday party on Saturday evening, because I have to meet an overseas visitor from Canada at 7; 00 p. m. on Saturday. I have really planned to celebrate your birthday and prepared a surprising present for you. It' s a pity that I can't say "Happy Birthday" to you in person. I know you are very kind and you will forgive me.
Although I can' t go to your birthday party, I' d like to express my congratulation to you "Happy Birthday". I hope you will have a good time together with your family and friends.
Best wishes!
Yours sincerely,
Wang Li