This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bleeding Disorders, Subject name: Pathology
Platelet aggregation is caused by? 
Select and explain. 
A. Nitrous oxide, B. Thromboxone A2, C. Aspirin, D. PGE2
B: Thromboxone A2
Answer: B: Thromboxone A2 
Explanation: Ans. (b). Thromboxone A2(Ref: Robbins 9th/pg 116-117)Thromboxone A2 (TXA2)It is produced by activated platelets and has prothrombotic propertiesIt is an Arachidonic acid metabolite of COX pathwayFunctions: It is a potent platelet aggregator & vasoconstrictorIts effect is neutralized by prostacyclin (PGI2)