Megan Is in the Mall, Looking at a Blue Sweater

Megan is in the mall, looking at a blue sweater. How does she know it's blue?

A) Blue/yellow opponent-process cells in the cortex increase their rate of firing.
B) Cones responsive to blue light in the retina begin responding.
C) Cones responsive to blue light in the retina begin responding, and blue/yellow opponent-process cells in the cortex increase their rate of firing.
D) Blue/yellow opponent-process cells in the retina begin responding, and cells responsive to blue in the occipital cortex increase their rate of firing.