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
Maximum permissible radiation dose in pregnancy is – 
Select and explain. 
A. 0.5 rad, B. 1.0 rad, C. 1.5 rad, D. 2 rad
A: 0.5 rad
Answer: A: 0.5 rad 
Explanation: Maximum permissible dose in pregnancy is 5 mSv (0.5 rem). 

Rem = Rad x Quality factor.

Main radiation exposure during pregnancy can be by X-rays (radiography or CT), and the quality factor of X-rays is 1. 
That means Rem = Rad.
Therefore, the maximum permissible dose in pregnancy is 0.5 rem or 0.5 rad.