This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fundamentals in Radiology, 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 is due to shift in sound frequency as the sound as reflected from the moving Red blood cells. If the motion of RBC is towards the transducer, the returning sound wave has higher frequency than transmitted wave. If the motion of RBC is away the transducer, the returning sound wave has lower frequency than transmitted wave. Color intenstiy indicates the relative velocity of the red blood cells.', 'role': 'assistant'}]