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: Pharmacology
[{'content': 'A patient of multidrug resistant tuberculosis is on antitubercular drugs. After a few months he develops an inability to distinguish between red and green color. Most likely drug causing these symptoms is : \nSelect and explain. \nA. Rifampicin, B. Ethambutol, C. Cycloserine, D. Ethionamide', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]