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
After-hyperpolarization during nerve conduction is due to: 
Select and explain. 
A. Slow entry of Na+, B. Pumping of Na+ outside, C. Slow entry of K+, D. Pumping of K+ outside
C: Slow entry of K+
Answer: C: Slow entry of K+ 
Explanation: The slow return of the K+ channels to the closed state also explains the after-hyperpolarization, followed by a return to the resting membrane potential.