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
Which of the following is not a feature of cardiac muscle? 
Select and explain. 
A. Tetany, B. All or none phenomenon, C. Pacemaker potential, D. Length-tension relationship
A: Tetany
Answer: A: Tetany 
Explanation: Tetany is not possible in cardiac muscle due to long refractory period