This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2019, Subject name: Pathology
Which of the following causes vasodilation? 
Select and explain. 
A. Thromboxane A2, B. Prostaglandin E2, C. Histamine, D. Serotonin
C: Histamine
Answer: C: Histamine 
Explanation: Major vasoactive amine responsible for vasodilation is Histamine. It causes dilation of aerioles and increases the permeability of venules. Prostaglandins can also cause vasodilation but major chemical responsible is histamine. Serotonin (5hydroxytryptamine) is a preformed vasoactive mediator present in platelets and ceain neuroendocrine cells, such as in the gastrointestinal tract, and in mast cells in rodents but not humans.