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': 'The colour of fluorescein staining in corneal ulcer is: \nSelect and explain. \nA. Yellow, B. Blue, C. Royal blue, D. Green', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Green', 'role': 'assistant'}]