英语 回信 .：要求宽泛 只要 回绝对方的晚会请求 就行 麻烦尽快

Dear...,
You invited me to your party tonight. I'd like to take part in it very much. But I'm very busy recently. I have to look after my grandmother. She is ill in bed for several days. So have to say "sorry" to you. Wish you have a good time.
Yours,
...

Dear__,
Thanks to your invitation. But I'm afraid that I've something urgent to deal with.
Wish you a good time!
yours,__.