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
[{'content': 'Which plasma protein is necessary for adhesion of platelets to subendothelialfibres? \nSelect and explain. \nA. Glycoprotein IIb, B. Von Willebrand factor, C. Platelet factor 3, D. Factor X', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Von Willebrand factor(Ref: Robbins 9th/pg 661)Von Willebrand factor is necessary for adhesion of platelets to subendothelial fibres.', 'role': 'assistant'}]