<prompt> Platelet adhesion to collagen occurs :Factor VIIIFactor IXvon Willebrand factorFibronectin  <response>: Platelet adhesion to collagen occurs von-Willebrand factorEndothelial 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. 