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: Ophthalmology
Tetracycline ointment for mass prophylaxis – 
Select and explain. 
A. 0.10%, B. 0.50%, C. 1%, D. 5%
C: 1%
Answer: C: 1% 
Explanation: In blanket antibiotic therapy, the regimen is to apply 1% tetracycline eye ointment twice daily for 5 days in a month for 6 months.