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
[{'content': 'Visual acuity is a test of: March 2004 \nSelect and explain. \nA. Light sense, B. Colour sense, C. Contrast sense, D. Form sense', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. Form sense', 'role': 'assistant'}]