This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
For color vision, which is true? 
Select and explain. 
A. Independent of wavelength of light, B. Depends on intensity discrimination, C. Involves opponent color cells, D. Minimum at fixation point
C: Involves opponent color cells
Answer: C: Involves opponent color cells 
Explanation: Ans. (c) Involves opponent color cells(Ref: Ganong, 25th ed/p. 191)Opponent process theory of color vision was proposed by HeringThis theory states that the three primary colors red, blue and green opposes one another so that the opponent color processing cell can't detect the presence of both colors at the same time