Mr Smith came back late by when all the guest had left.

题目

Mr Smith came back late by when all the guest had left.
by when 是怎么回事,是引导定语从句吗?

答案

Mr Smith came back late by (when all the guest had left).
by引导的时间状语,这个时间状语是when 引导的从句
Smith先生回来得很晚,那时所有的客人都离开了.