This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiotherapy, Subject name: Radiology
[{'content': 'The radiation unit used to for effective dose is: \nSelect and explain. \nA. Rad, B. Rem, C. Sievert, D. Gray', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C. SievertQuantityOld unitNew SI unitActivityCurieBecquerelExposureRoentgenCoulomb/kgAbsorbed doseRadGrayDose equivalentRemSievert', 'role': 'assistant'}]