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': 'Functional efficiency of lacrimal drainage system may be assessed by: \nSelect and explain. \nA. Lacrimal syringing, B. Subtraction macrodacryocystography, C. Radionucleotide dacryocystography, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Radionucleotide dacryocystography', 'role': 'assistant'}]