This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ULTRASOUND, Subject name: Radiology
[{'content': 'Doppler effect results from change in- \nSelect and explain. \nA. Amplitude of sound, B. Frequency of sound, C. Direction of sound, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Doppler effect: change in frequency because of relative motion between moving source of sound and observer. Example: Sound waves hitting resting parenchyma Sound wave hitting moving RBC The difference gives color coding doppler effect. Color coding: based on direction of flow Flow TOWARDS probe: RED Flow AWAYfrom probe:BLUE Color does NOT depend on aery or vein Intensity of color depends on velocity of flow', 'role': 'assistant'}]