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: Surgery
All of the following are derivatives of connective tissue except 
Select and explain. 
A. Endothelial cells, B. Clara cells, C. Fibroblast, D. Mast cells
B: Clara cells
Answer: B: Clara cells 
Explanation: Clara cells: are present in lining of respiratory bronchioles and seems to secrete a variety of products including clara cells secretory protein (CSCP) and a component of the lung surfactant. They are also responsible for detoxifying harmful substances inhaled into lungs. Clara cells are pa of respiratory system which is derived from endoderm, while options (a), (c) and (d) are derived from connective tissue, which is developed from mesoderm.