The three sets of color receptors within the retina are sensitive to wavelengths of visible light are: select one: a. red, green, and yellow b. orange, green and purple c. red, blue and yellow d. blue, green and red

D

Explanation:

These colors are also referred to as primary colors. When mixed in different proportions, they can produce a variety of secondary and tertiary colors and this is how the human eye is also to perceive many colors even with only these three eye pigments.  

that is wrong, its not thymus.

looks like the answer is     c     to me!