Dear Bob,

How are you doing? We planned to go to the bookstore this Saturday. Unfortunately, I can’t make it.So, I am writing to express my heartfelt apology to you.

How I wish I could go with you! However, I am chosen to represent our school to take part in the English debate competition with an America high school, which, you know, is of great importance to me, for I have always been dreaming to have a chance like this to improve my spoken English. As a result, I have no choice but to say sorry to you.

How about going to the bookshop this Sunday? Then both of us will be available and I can share my experience of the competition with you. Please. I am looking forward to your reply.

Yours,

LiHua