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
Calcium channel blocker with maximum effect on conduction in heart is: 
Select and explain. 
A. Phenylamine, B. Nifedipine, C. Diltiazem, D. Verapamil
D: Verapamil
Answer: D: Verapamil 
Explanation: None