Which of the Following Explains the Unknown Quadrant Found in the Johari

Which of the following explains the unknown quadrant found in the Johari window?

A) It is hypothetical but probably nonexistent for most people.
B) It is fairly large for people who are introspective.
C) It represents that part of yourself that others are aware of but you are not.
D) It represents information about yourself that you and others have yet to discover.