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
Young Helmholtz theory is associated with which of the following? 
Select and explain. 
A. Colour vision, B. Nerve conduction, C. Nerve conduction, D. None of the above
A: Colour vision
Answer: A: Colour vision 
Explanation: The Young-Helmholtz theory of color vision in humans postulates the existence of three kinds of cones, each containing a different photopigment and that are maximally sensitive to one of the three primary colors, with the sensation of any given color being determined by the relative frequency of the impulses from each of these cone systems. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 12.