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': 'The preferred treatment option for primary syphilis is : \nSelect and explain. \nA. Injection Benzathine pencillin 2.4 million units IM single dose, B. Injection Benzathine penicillin 2.4 million units IM Once a week for 3 weeks, C. Cap. Doxycycline 100 mg orally twice a day for 2 weeks, D. Tab. Azithromycin 2 gin single dose', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]