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: Physiology
[{'content': 'On increasing, vagal tone following occurs in pacemaker \nSelect and explain. \nA. Increased Na+, increased slop, B. Decreased Na+, decreased slop, C. Increased Na+, decreased slop, D. Decreased Na+, increased slop', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Na+ influx causes the pacemaker potential (prepotential). Due to vagal stimulation, the Na+ influx decreases, this leads to a decrease in the slop of prepotential.', 'role': 'assistant'}]