This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetus, Subject name: Gynaecology & Obstetrics
[{'content': 'Maximum dose of radiation exposure during pregnancy is \nSelect and explain. \nA. 0.5 rad, B. 1 rad, C. 1.5 rad, D. 5 rad', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The biological effects of x-rays are caused by an electrochemical reaction that can damage tissue. Embryo-fetal risks from low-dose diagnostic radiation appear to be minimal. Current evidence suggests that there are no increased risks for malformations, growth restriction, or aboion from a radiation dose of less than 0.05 Gy (5 rad). Reference: William&;s Obstetrics; 24th edition; Chapter 46; General Considerations and Maternal Evaluation', 'role': 'assistant'}]