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
A  vasodilator is obtained after decarboxylation of: 
Select and explain. 
A. Histidine, B. Arginine, C. Tyrosine, D. Glycine
A: Histidine
Answer: A: Histidine 
Explanation: Histidine on decarboxylation gives histamine which is a vasodilator.