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
Amount of radioactivity absorbed by body is measured by: March 2010 
Select and explain. 
A. Curie, B. Roentgen, C. Rad, D. Rem
C: Rad
Answer: C: Rad 
Explanation: Ans. C: Rad