Question

a sound wave travels through air. in which regions are air molecules the least dense?
compressions
frequencies
pitches
rarefactions

Explanation:

Sound waves are longitudinal waves. In a longitudinal wave traveling through air, compressions are regions where air molecules are close together (high - density), and rarefactions are regions where air molecules are spread apart (low - density). Frequency is a measure of how many wave cycles occur per second, and pitch is related to the frequency (a perceptual quality). So, the regions with the least - dense air molecules are rarefactions.

Answer:

D. rarefactions