What is the function of von Willebrand's factor?
a) membrane protein that binds thrombin to initiate activation of protein C
b) produced following endothelial activation by substances such as cytokines, endotoxin, thrombin, immune complexes and mitogens
c) released following endothelial exposure to substances such as thrombin, histamine, and fibrin
d) maintains vascular relaxation and inhibits platelet adhesion and activation
