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: Pathology
Von Willebrand's factor is synthesized in which one of the following - 
Select and explain. 
A. Vascular endothelium, B. Macrophages, C. Liver, D. Eosinophils
A: Vascular endothelium
Answer: A: Vascular endothelium 
Explanation: None