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
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: 
Select and explain. 
A. Rifampicin, B. Ethambutol, C. Isoniazid, D. Streptomycin
B: Ethambutol
Answer: B: Ethambutol 
Explanation: Ans. B. EthambutolEthambutol is first line antitubercular drug which is contraindicated in children as it causes optic neuritis and red-green color blindness.