Theorie:
Relative clauses. Clauses with who/that/which. Part 2
You must use who/that/which when you refer to the subject of the relative clause.
Sometimes who/that/which is the object.
Have you found the keys that you lost?
1. When who/that/which is the object, you can drop it.
The woman I wanted to see was away.
The dress Kate bought doesn’t fit her very well.
2. Note the position of prepositions (in/to/for) in relative clauses:
Are these the books you were looking for?
The woman he fell in love with left him after a month.
3. You cannot use what in the following sentences:
Everything (that) they said was true.
I gave her all the money (that) I had.
What = ‘the thing(s) that’.
Did you hear what he said? (= the things that he said)