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 are aeriolar dilators except ? 
Select and explain. 
A. Hydralazine, B. Minoxidil, C. Nitrates, D. Nifedipine
C: Nitrates
Answer: C: Nitrates 
Explanation: Ans. is 'c' i.e., Nitrates