On...class, I was late for ...mintues, because ...emergency.
I understand that I do not have a good record on this, but this time I really could not make it. I feel sincerely sorry about that I did not show up on time, but that was not entirely my fault.
接下来解释到底发生了什么
不管什么只要写的坦诚就好
Nevertheless, I am responsable for my attendence. There is no excuse that I would be late for the same reason again. There is a Chinese old saying that "mistakes make men wiser". I will learn someting from this. I will never make the same mistake again.
Please forgive me.