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
Functional efficiency of lacrimal drainage system may be assessed by: 
Select and explain. 
A. Lacrimal syringing, B. Subtraction macrodacryocystography, C. Radionucleotide dacryocystography, D. All of the above
C: Radionucleotide dacryocystography
Answer: C: Radionucleotide dacryocystography 
Explanation: Ans. Radionucleotide dacryocystography