This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'Acute symptomatic sinus bradycardia usually responds to- \nSelect and explain. \nA. Adrenalinea, B. Dopamine, C. Atropine, D. Norepinephrines', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Sinus bradycardia: A regular but unusually slow hea beat (50 beats/minute or less at rest). Fainting can occur with sinus bradycardia if the hea slows down even more. This can occur, for example, when the vagus nerve sends a signal to the hea that suddenly drops the hea rate Ref Harrison 20th edition pg 1456', 'role': 'assistant'}]