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: Medicine
[{'content': 'In ethambutol toxicity there will be loss of ability to see which of the following colour? \nSelect and explain. \nA. Red, B. Green, C. Blue, D. Yellow', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Optic neuritis, the most serious adverse effect repoed, typically presents as reduced visual acuity, central scotoma, and loss of the ability to see green (or, less commonly, red). Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 1376.', 'role': 'assistant'}]