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: Social & Preventive Medicine
What is the recommended drug for treatment of carriers of diphtheria? 
Select and explain. 
A. Oral penicillin, B. Injectable penicillin, C. Azithromycin, D. Erythromycin
D: Erythromycin
Answer: D: Erythromycin 
Explanation: Carriers of diphtheria should be treated with a 10 days course of erythromycin. Ref: Park 21st edition, page 151.