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: Physiology
Endothelial cells synthesize: 
Select and explain. 
A. Fibrinogen, B. Von Willebrands Factor, C. Factor-X, D. Factor-XII
B: Von Willebrands Factor
Answer: B: Von Willebrands Factor 
Explanation: Von Willebrands Factor