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: Pharmacology
[{'content': 'Treatment of choice in solar keratosis is : \nSelect and explain. \nA. Methotrexate, B. Topical 5 FU, C. Topical mechlorethamine, D. Topical steroids', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Solar (actinic) keratosis is treated by application of liquid nitrogen. The alternative is 5-FU. Imiquimod cream can also be used.', 'role': 'assistant'}]