EF5/6 adjective clauses

who that which

whom - NOT IMPORTANT. FORGET IT!!
VERY FORMAL, FANCY

"The woman who I was talking to is my good friend."

who  object

"The woman whom I was talking to is my good friend."

This is the person whom I was telling you about.

This is the person who I was telling you about.

This is the person who I was telling you about.

This is the person I was telling you about. MOST NATURAL

To whom it may concern,
To whom it might concern, X
For whom it may concern, X


WHOSE - possession, own something

I my, you your, she her, we our

"The boy was angry."
"The boy whose bicycle was stolen was angry. He became the greatest boxer of his generation."

"I whose phone was broken had to buy a new one." X Can't use 'whose' with a pronoun.
"Sarah whose phone was broken had to buy a new one."