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': 'Minimum angle of resolution when visual acuity is 6/6 \nSelect and explain. \nA. 1 min of arc, B. 5 min of arc, C. 10 min of arc, D. 15 min of arc', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer-A. 1 min of arcVisual acuity is the first test performed after taking history.Measurement of the central visual acuity is essentially an assessment of function of the fovea centralis.An object must be presented so that each poion of it is separated by a difinite interval, known as minimum angle of resolution (MAR). Customarily, this interval has become one minute of an arc.The test object should subtends an angle of five minutes of an arc.', 'role': 'assistant'}]