Consider the following:
I. The speed of the observer;
II. The speed of the source;
III. The loudness of the sound.
In the Doppler effect for sound waves, which factors affect the frequency that the observer hears?
1. B only
2. None of these
3. C only
4. A only
5. A, B, and C
6. A and C only
7. B and C only
8. A and B only