This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Surgery
[{'content': 'Investigation using dye to find out stone in salivary gland \nSelect and explain. \nA. Sialography, B. Mammography, C. MR angiography, D. USG', 'role': 'user'}, {'content': "Answer: A \nExplanation: Dye used is lipiodol or sodium diatrizoate(Hypaque).24-gauge cannula is passed into either Stenson's duct or Whaon's duct and one ml of the dye is injected into the duct and X-ray is taken. SRB,5th,406.", 'role': 'assistant'}]