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
Only drug used in pregnancy with syphilis ? 
Select and explain. 
A. Penicillin, B. Clinadmycin, C. Azithromycin, D. Erythromycin
A: Penicillin
Answer: A: Penicillin 
Explanation: Ans. is'a'i.e., Penicillin[Ref: Harrisons 18th/e p. 1j871Management of Syphilis in Pregnancy:Penicillin is the only recommended agent for the treatment of syphilis in pregnancy.If the patient has a documented penicillin allergy, desensitization and penicillin therapy should be undeaken according to the CDC's 2010 guidelines.