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
Antibiotic which is effective as a single dose therapy for trachoma is : 
Select and explain. 
A. Doxycycline, B. Clarithromycin, C. Azithromycin, D. Erythromycin
C: Azithromycin
Answer: C: Azithromycin 
Explanation: None