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': 'Characteristic fallopian tube findings on sonography in pelvic inflammatory disease includes all except \nSelect and explain. \nA. Fallopian tube wall thickening., B. Cog-wheel appearance in cross-section., C. Color doppler shows less vascularity., D. Distended tube filled with echogenic fluid.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Color doppler shows marked vascularity with low-impedance blood flow which reflects hyperemia.', 'role': 'assistant'}]