This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Obstetrics And Gynaecology, Subject name: Radiology
Which of the following is associated with the least radiation in pregnancy? 
Select and explain. 
A. X-ray, B. MRI, C. CTscan, D. VQscan
B: MRI
Answer: B: MRI 
Explanation: Ans: b (MRI) Ref: Practical Radiotherapy- physics ami equipment 2nd ed/p.68MRI uses magnetic properties of hydrogen atoms to generate images.Increasing order of radiation:-X-ray< VQ scan < CT scan.