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
[{'content': 'Ultra-structurally, endothelial cells contain: \nSelect and explain. \nA. Weibel Palade bodies, B. Langerhan’s granules, C. Abundant glycogen, D. Kallikrein', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Endothelial cells are the major\xa0source of plasma vWF, whereas most factor VIII is synthesized in the liver. vWF is found in the plasma (in association\xa0with factor VIII), in platelet granules, in endothelial cells\xa0within cytoplasmic vesicles called\xa0Weibel-Palade\xa0bodies,\xa0and in the subendothelium, where it binds to collagen.\nReference-Robbins BASIC PATHOLOGY 10th edition pg-490', 'role': 'assistant'}]