This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Obstetrical Ultrasonography in the First Trimester, Subject name: Radiology
[{'content': 'T sign is seen in - \nSelect and explain. \nA. Genital TB, B. Membrane in twin pregnancy, C. Molar pregnancy, D. Choriocarcinoma', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Membrane in twin pregnancyo 'T sign' refers to appearance of the inter-twin membrane in a monochorionic twin pregnancy.", 'role': 'assistant'}]