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': 'In retinoscopy for refractive error at lm we add -1 D. If done at a distance of 66 cm, the addition factor will be: \nSelect and explain. \nA. -2D, B. -1.5 D, C. -0.5 D, D. -5 D', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. -1.5 D', 'role': 'assistant'}]