This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Magnetic Resonance Imaging, Subject name: Radiology
[{'content': 'MRI magnet is a \nSelect and explain. \nA. Ferromagnet, B. Paramagnet, C. Simple magnet, D. Superconducting-magnet', 'role': 'user'}, {'content': 'Answer: D \nExplanation: MRI uses a Superconducting magnet which is kept cool using Helium. A superconducting MRI magnet comprises a steel cryostat with the superconducting coils immersed in liquid helium at 4.2 Kelvin (-269degC or -452degF).', 'role': 'assistant'}]