Question

在定语从句中，who，which什么时候可以省略

Answer 1

who不能省略，但是作宾语时whom可以省略，如
He is the man （whom） I saw yesterday. 他就是我昨天见到的那个人。
which在定语从句中作宾语时可省略，如
The package (which) you are carrying is about to come unwrapped.你拿那个包裹快要散开了。
但是当which位于介词后面时则不能省略，如
I still remember the day on which I first came to school. 我仍然记得初来学校的那一天。