The "Qualia Problem" That This Reading Refers to Is That

The "qualia problem" that this reading refers to is that

A) You can never know if the red you see is the same as the red someone else sees.
B) Our understanding of the world is limited by our human senses.
C) It is hard for a dualist view of the world to account for qualia.
D) It is hard for a physicalist view of the world to account for qualia.