What is the best description of sound waves?
A. A source vibrates up and down, causing air molecules to move up and down perpendicular to the direction the wave is transmitted.
B. A source vibrates back and forth, causing air molecules to move back and forth in the same direction that the wave is transmitted.
C. A source vibrates up and down and back and forth, causing air molecules to move in a circular motion as the wave is transmitted.
D. A source ejects a ring of high-velocity air molecules that travel from the source to a listener.