This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
[{'content': 'Lactating women with painful breast, 1st investigation to be done should be NOT RELATED-SURGERY \nSelect and explain. \nA. USG, B. Mammography, C. CT, D. MRI', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]