Patients with Von Willebrand Disease Have Abnormal Bleeding Tendency of Varying

Patients with von Willebrand disease have abnormal bleeding tendency of varying severity.The process that is most directly abnormal in these patients is:

A) Adhesion of platelets to the extracellular matrix.
B) The synthesis of g-carboxyglutamate containing clotting factors.
C) Contact phase activation.
D) The extrinsic pathway of blood clotting.
E) The cleavage of prothrombin to thrombin.