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': 'The middle cardiac vein is located in the: \nSelect and explain. \nA. Anterior interventricular sulcus., B. Posterior interventricular sulcus., C. Posterior AV groove., D. Anterior AV groove.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The middle cardiac vein commences at the apex of the hea; ascends in the posterior longitudinal sulcus, and ends in the coronary sinus near its right extremity.', 'role': 'assistant'}]