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
Tetracyclines ointment for mass prophylaxis 
Select and explain. 
A. 1%, B. 0.10%, C. 0.50%, D. 5%
A: 1%
Answer: A: 1% 
Explanation: Tetracyclines:
These are broad-spectrum bacteriostatic agents with considerable action against both gram-positive and gram-negative organisms as well as some fungi, rickettsiae and chlamydiae.
This group includes tetracycline, chlortetracycline and oxytetracycline.