dear wang fang,

　　thank you so much for your kind invitation to spend the summer holidays with you. it was very good of you to invite me, but i`m sorry to say that i shall not be able to go. i will tell you why. first of all, my mother is seriously ill. and my father is always busy with his work. i shall have to look after my mother and do some housework.

　　thank you again for your invitation.

　　yours sincerely

　　xiao hong