Question

Those are the things ___________ I lost in the street yester

Answer 1

Those are the things _____ I lost in the street yesterday.

句中lost少宾语,有先行词things,which、that均可,但句首those,所以只能用that.

He is the doctor __ we often talk about.

有先行词,且充当talk about的宾语,who、whom、that、不填均可.