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: Anatomy
[{'content': 'Branches of R.C.A. (Rt. Coronary aery): \nSelect and explain. \nA. Obtuse marginal, B. Acute marginal, C. Diagonal, D. All', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B. i.e. Acute marginal', 'role': 'assistant'}]