This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'All of the following promote platelet aggregation except \nSelect and explain. \nA. Plasmin, B. Prostacyclin, C. Thrombospondin, D. Platelet activating factor', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Factors inhibiting platelet aggregation are ATP, PGI2 or prostacyclin, Aspirin, coisol Factors oring platelet aggregation are Thrombospondin which helps in fixation of platelet, platelet activating factor, ADP, Thromboxane A2, Ca2+,vWF etc. Plasmin also helps in platelet aggregation. Ref: Textbook of medical physiology by N Geetha, 2nd edition, page no.102,103', 'role': 'assistant'}]