Maximum permissible radiation dose in pregnancy is –: (A) 0.5 rad, (B) 1.0 rad, (C) 1.5 rad, (D) 2 rad
Answer is A. 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.