Can you explain how it came about that you were an hour late哪位高手能_英语解答

Can you explain how it came about that you were an hour late
哪位高手能帮我解释下这句话是什么从句,分析下哈,

人气：134 ℃　时间：2019-10-24 06:17:40

解答

how引导宾语从句.作为explain的宾语.
it...that属于虚拟主语,you were an hour late也算是主语从句.