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: Anatomy
[{'content': 'All of the following are derivatives of connective tissue except? \nSelect and explain. \nA. Endothelial cells, B. Clara cells, C. Fibroblast, D. Mast cells', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]