This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
[{'content': 'Radiation dose safe in pregnancy is \nSelect and explain. \nA. 1 rad, B. 5 rads, C. 50 rads, D. 500 rads', 'role': 'user'}, {'content': 'Answer: B \nExplanation: (Ref: Farr&;s physics for medical imaging 2e,39)', 'role': 'assistant'}]