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: Radiology
[{'content': 'Amount of radioactivity absorbed by body is measured by: March 2010 \nSelect and explain. \nA. Curie, B. Roentgen, C. Rad, D. Rem', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: Rad', 'role': 'assistant'}]