This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Platelet adhesion to collagen occurs : 
Select and explain. 
A. Factor VIII, B. Factor IX, C. von Willebrand factor, D. Fibronectin
C: von Willebrand factor
Answer: C: von Willebrand factor 
Explanation: Platelet adhesion to collagen occurs von-Willebrand factor)Endothelial injury allows platelets to contact the underlying extracellular matrix; subsequent adhesion occurs through interactions with von Willebrand factor (vWF), which is a product of normal endothelial cells and an essential cofactor for platelet binding to matrix elements.