Final answer:
The frequency of the sound from a stationary source remains unchanged when you move twice as far away, although the intensity decreases. So the correct option is d.
Step-by-step explanation:
When considering a sound source emitting waves uniformly in all directions, if you move to a point twice as far away from the source, the frequency of the sound will remain unchanged. The frequency of a wave is the number of cycles per second and is dependent on the source of the sound, not the distance from it. However, as you move away from the sound source, while the frequency remains constant, the intensity of the sound will decrease according to the inverse square law. This means that at double the distance, the intensity would be one-fourth, but the frequency you perceive does not change.
The Doppler Effect explains changes in frequency perception, but it requires relative motion between the source and the observer. In a case where both the source and observer are stationary, or if the observer is moving directly away or towards the source at a constant velocity, the frequency perceived by the observer is the same as the source's emission frequency.