Dear Mr.Green:
I really appreciate you inviting me to join your party.
I,d love to go but I am sorry to say that I can't make it,because I,ve already mapped out what I will do this Saturday.My cousin Li Mei,who left home for Australia for further studies last year,informed me that she would be returning this Saturday morning and asked me to pick her home up at the airport.
最后一段自己来吧
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