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
Action of Nitroglycerin is 
Select and explain. 
A. Direct action on smooth muscle, B. Slows SA node conductvity, C. Blocks arrhythmia, D. Increases perfusion to heart
A: Direct action on smooth muscle
Answer: A: Direct action on smooth muscle 
Explanation: None