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: Medicine
[{'content': 'Clubbing is least common in - \nSelect and explain. \nA. Squamous cell carcinoma, B. Adenocarcinoma, C. Small cell carcinoma of lung, D. Mesothelioma', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]