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
The preferred treatment option for primary syphilis is : 
Select and explain. 
A. 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
A: Injection Benzathine pencillin 2.4 million units IM single dose
Answer: A: Injection Benzathine pencillin 2.4 million units IM single dose 
Explanation: None