I did not see the film last night.That was ____ I had to help my _英语解答

I did not see the film last night.That was ____ I had to help my brother with his homework.
请问这里要填什么

人气：450 ℃　时间：2020-03-26 21:49:24

解答

because
请及时采纳,多谢!那that引导的这个是什么句子呢？此句本身是主系表结构意在解释没看电影的原因。那这是表语从句吗？表语从句不是不能用because引导吗？是的。所以这道题有点怪。