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: Unknown
[{'content': 'Neurotransmitter employed by rods and cones is \nSelect and explain. \nA. Dopamine, B. Serotonin, C. Glutamate, D. Nitric oxide', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]