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
The pacemaker potential is due to: 
Select and explain. 
A. Fast Na+ channel, B. Decrease in K+ permeability, C. Slow Ca++ channel, D. Rapid repolarization
B: Decrease in K+ permeability
Answer: B: Decrease in K+ permeability 
Explanation: Pacemaker potential is due to slow Na+ >> Rapid Ca++  >> decrease K+ permeability. So, with the provided  options, best answer is decrease K+ permeability.