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
[{'content': 'Tetracyclines ointment for mass prophylaxis \nSelect and explain. \nA. 1%, B. 0.10%, C. 0.50%, D. 5%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Tetracyclines:\nThese are broad-spectrum bacteriostatic agents with\xa0considerable action against both gram-positive and gram-negative organisms as well as some fungi,\xa0rickettsiae and chlamydiae.\nThis group includes\xa0tetracycline, chlortetracycline and oxytetracycline.', 'role': 'assistant'}]