请根据下面所给的题目和情景,用英语写出一篇不少于80词的短文.

A Letter of Apology
Dear A
I am very sorry that I could not meet you last night.I hope that you did not wait too long outside the Beijing Theatre.I had to look after my small brother until my mother returned home.She was a long time at the doctor's and,she arrived home very late.I ran all the way to the bus-stop.,but I had already missed the bus.I decided to get on a tram and I arrived at the Beijing Theatre at eight o' clock.I did not think that you would still be there because I was three-quarters of an hour late.I do hope that you will forgive me.
Your friend,
B
(注：A、B可替换为具体名字)