This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Women Imaging, Subject name: Radiology
[{'content': 'Investigation of choice for a pregnant lady with upper abdominal mass is \nSelect and explain. \nA. USG, B. X-ray, C. CT, D. MRI', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ultrasound is the most commonly used imaging exam during pregnancy. It usually focuses on the baby in the womb. When ultrasound does not provide a clear answer, or if other pas of your body need to be imaged, an MRI is usually performed. MRI does not use x-rays.', 'role': 'assistant'}]