This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
All of the following are examples of primary colours, EXCEPT: 
Select and explain. 
A. Red, B. Green, C. Blue, D. None of the above
D: None of the above
Answer: D: None of the above 
Explanation: The sensation of white, any spectral color, and even the extraspectral color, purple, can be produced by mixing various propoions of red light (wavelength 723-647 nm), green light (575-492 nm), and blue light (492-450 nm). which are therefore called the primary colors. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 12.