What was it that you did not come to class yesterday?怎么翻译

问题描述:

What was it that you did not come to class yesterday?怎么翻译

这句子里的 it 是作为 the reason 的替代,在口语中有时候会如此说.
What was the reason that you did not come to class yesterday?
意思就清楚啦,你昨天没来上课是什么原因?