It was because the traffic was very heavy during the rush hour,I was late again.

问题描述:

It was because the traffic was very heavy during the rush hour,I was late again.
这句话对吗?我认为应该把“,”改成that

嗯,有道理,既然有“it was”在句首就是要使用强调句的,应该换成that.
(不过可以改的简练点:it was because of the heavy triffic during the rush hour that i was late again)