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: Unknown
[{'content': 'Delta-sign is seen in- \nSelect and explain. \nA. Petrositis, B. Acute mastoiditis, C. sigmoid sinus thrombosis, D. Glomus tumor', 'role': 'user'}, {'content': 'Answer: C \nExplanation: (Refer: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 92)\n\nContrast-enhanced CT scan can show sinus thrombosis by typical delta-sign.\xa0 It is a triangular area with rim enhancement, and central low density area is seen in posterior cranial fossa on axial cuts\nDelta-sign may also be seen on contrast enhanced MRI', 'role': 'assistant'}]