This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contrast Agents, Subject name: Radiology
[{'content': 'Which of the following is an Ionic dimer? \nSelect and explain. \nA. Diatrizoate, B. Metrizoate, C. Ioxaglate, D. Iothalamate', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Example of Ionic Monomers - UROGRAFFIN, GASTROGRAFFIN, Diatrizoate, lothalamate Example of Ionic Dimers- -Ioxaglate Example of Non-Ionic Monomer - Iohexol, Ioleron, Iopamidol, Ipromide, Ioversol, Xenetix Example of Non-Ionic Dimer - Iodixanol, Iotrolan', 'role': 'assistant'}]