This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inflammation, Subject name: Pathology
Which one of the following is NOT true about chemical mediators: 
Select and explain. 
A. Leukotrienes are formed by lipo-oxygenase pathway, B. Histamine is a preformed chemical mediator, C. Prostaglandin causes vasoconstriction at the site of inflammation, D. Thromboxane A2 is associated with platelet aggregation
C: Prostaglandin causes vasoconstriction at the site of inflammation
Answer: C: Prostaglandin causes vasoconstriction at the site of inflammation 
Explanation: Leukotrienes are formed by Lipo-oxygenase , Whereas, prostaglandins are formed by cyclo-oxygenase. PGs causes vasodilation.