This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'A lady with CA ovary in follow up with raised CA 125 level, Next step: \nSelect and explain. \nA. CT, B. PET, C. MRI, D. Clinical exam and serial follow up of CA 125', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]