What Is the Probable Cause for Thrombotic Thrombocytopenic Purpura

What is the probable cause for thrombotic thrombocytopenic purpura?

A) deficiency of a metalloprotease needed to enzymatically degrade unusually large von Willebrand factor (VWF) multimers
B) abnormal synthesis of unusually large VWF multimers by endothelial cells
C) abnormal synthesis of unusually large VWF multimers by megakaryocytes
D) abnormal complexing of normal VWF multimers to create unusually large VWF multimers