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: Pharmacology
All of the following drugs act by blocking calcium channels except: 
Select and explain. 
A. Dantrolene, B. Nicardipine, C. Diltiazem, D. Verapamil
A: Dantrolene
Answer: A: Dantrolene 
Explanation: None