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
[{'content': 'Which one of the following is NOT true about chemical mediators: \nSelect and explain. \nA. 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', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Leukotrienes are formed by Lipo-oxygenase , Whereas, prostaglandins are formed by cyclo-oxygenase. PGs causes vasodilation.', 'role': 'assistant'}]