假如你叫李华，你北京的法国朋友Jack邀请你，和他一起去云南旅行，但你因故不能参加。请你根据以下要点给他写一封Email：
1. 表达想参加的意愿;
2. 忙于准备考试;
3. 由于感冒,身体不适;
4. 表示歉意并另约时间。
注意：1.词数120左右;

2.信中不能出现与本人相关的信息;

3.信的开头与结尾已为你拟好,不计入总词数。

Dear Jack,

I’m terribly sorry to tell you that I am unable to go to Yunnan with you.

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Yours,

Li Hua