Respostas
He bought all the tools which are required to fix his old car.
This is the doctor who helped Sara recover from her illness.
This is the girl whom he fell in love with.
She managed to pass the exams in spite of all difficulties. Which didn't surprise people who knew her.
These are the kids whose parents were arrested.
Give me the plate which is in the table.
Se você quiser aprender a utilizar, eu vou te dar um macete:
Who: sempre vai ser um sujeito, vai estar realizando uma ação.
ex: He is the one who dared to invade our land.
Whom: É um objeto, nesse caso não realiza ação e geralmente é usado como citação.
ex: This is the man whom you told me about.
Whose: Simboliza posse, nesse caso um objeto pertence ao sujeito.
The man whose pants were red.
Which: Um objeto específico.
Bring me the knife which is in the drawer.