"Who" is a subject pronoun, while "whom" is an object pronoun. This means that "who" should be used when referring to the person doing the action, while "whom" should be used when referring to the person receiving the action.
The girl who sits next to you in class always wears colorful socks.
The woman whom I presume to be her mother doesn't seem to like them.
The technician ___ I asked
for assistance was helpful.
She is the kind of person for
___ family is important.
My dad will accept ___ever I
choose as my wife.
I just want to know ___ made
this beautiful artwork.
To ___ have you offered the
car?
___ gave you permission to
get into this car?
Tell me, ___ told you that?
For ___ are you buying the
flowers?
Do you know the man ___ is
standing on the chair?
___ wrote that book?
The technician whom I asked
for assistance was helpful.
She is the kind of person for
whom family is important.
My dad will accept whomever I
choose as my wife.
I just want to know who made
this beautiful artwork.
To whom have you offered the
car?
Who gave you permission to
get into this car?
Tell me, who told you that?
For whom are you buying the
flowers?
Do you know the man who is
standing on the chair?
Who wrote that book?
