Which word is used INCORRECTLY in the following sentence?
My father, from who I have learned so much, has had an immense effect on my career as a nurse.

“Who” should be used to refer to the subject of a sentence.
“Whom” should be used to refer to the object of a verb or preposition.
Since “who” is an object of the preposition (from), we must use “whom.”
If you can replace the word with “he” or “she”, use “who.” If you can replace it with “him” or “her,” use “whom.”