This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Which one is true about serotonin? 
Select and explain. 
A. Sleep suppressant, B. Increase appitite, C. Vasoconstriction, D. Bronchodialtion
C: Vasoconstriction
Answer: C: Vasoconstriction 
Explanation: Serotonin is a powerful vasoconstrictor, produces hyperpnea, increases tone of smooth muscle of intestine, bronchioles.(Ref: Textbook of physiology N Geetha 2nd edition page no.446)