This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Radiology
[{'content': 'Lambda sign on ultrasound is seen in? \nSelect and explain. \nA. Ectopic pregnancy, B. Twin pregnancy, C. Hyaditiform mole, D. Fibroid', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans BTwin peak sign (also known as the lambda (l) sign) is a triangular appearance of the chorion insinuating between the layers of the intertwin membrane and strongly suggests a dichorionic twin pregnancy.', 'role': 'assistant'}]