This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2019, Subject name: Pathology
Von Willebrand factor is secreted by which of the following? 
Select and explain. 
A. Macrophages, B. Endothelial cells, C. Platelets, D. Fibroblast
B: Endothelial cells
Answer: B: Endothelial cells 
Explanation: Endothelial cells contain intracellular stores known as WeibelPallad bodies which contain Von-willebrand factor and P-selectin.