This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Anatomy
[{'content': 'Least common cause of clubbing \nSelect and explain. \nA. Adenocarcionma, B. Squamous cell carcinoma, C. Small cell carcinoma, D. Mesothelioma', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Clubbing is most common with adenocarcinomaand is least common with small lung cell cancer... Ref:Ptinciples and practice of lung cancer Pg 348', 'role': 'assistant'}]