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': 'Exfoliative cytology is indicated in \nSelect and explain. \nA. Heavily keratinized lesions of oral cavity, B. Pre-cancerous lesions of oral cavity, C. Cigarette smokers, D. Mass screening of cervical cancer', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]