This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti Microbial, Subject name: Pharmacology
[{'content': 'A patient of MDR Tb is on anti-tubercular drugs. After few months, he develops red-green color blindness. Most likely drug causing this symptom is: \nSelect and explain. \nA. Rifampicin, B. Ethambutol, C. Isoniazid, D. Streptomycin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. EthambutolEthambutol is first line antitubercular drug which is contraindicated in children as it causes optic neuritis and red-green color blindness.', 'role': 'assistant'}]