This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Hyperpolarization is caused by which ions 
Select and explain. 
A. K+, B. Na+, C. Ca++, D. HCO3
A: K+
Answer: A: K+ 
Explanation: Slow return of the K+ channels to the closed state causing hyperpolarization.(Ref Textbook of physiology AK Jain 5th edition page no.36)