Answer:
B. The gas must release heat to its surroundings.
Explanation:
Since the process is reversible , it must be slow . Since temperature is kept constant so the internal energy is constant , Since volume is decreased , pressure must be increased. Since work is done on the gas ( gas is compressed ) , so heat must be released by the gas so that its internal energy remains constant.
1 - Vibrate east and west
Sound waves are <em>longitudinal waves</em>, that means the vibrations are parallel to the direction of energy transfer. If the energy transfer is going East, then the vibrations will be East and West creating compressions and rarefactions in the air.