This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
[{'content': 'SA Node is located at \nSelect and explain. \nA. Upper end crista terminalis, B. Lower end of crista terminalis, C. At opening of IVC, D. At ostium primum', 'role': 'user'}, {'content': "Answer: A \nExplanation: SA node is situated at the atriocaval junction in the upper pa of the sulcus terminalis B D CHAURASIA'S HUMAN ANATOMY UPPER LIMB THORAX-VOLUME 1 SIXTH EDITION Page no-262", 'role': 'assistant'}]