题目内容：

Tom邀请Li Ming参加他这个周日的生日宴会, 但Li Ming的父母出差了, 要到下个月才回来, 奶奶又卧病在床, 需要人照顾。另外, 英语考试即将来临。因此, Li Ming无法前去参加生日宴会。Li Ming感到很抱歉, 只好写信辞谢。

　　根据提示写一封60~80个词的信。

Dear Tom,

Thank you very much for inviting me to your birthday party. I’d love to go but I can’t. My parents are 

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Li Ming