Question

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

Explanation:

• Compressions: In a sound wave, compressions are regions where air molecules are close together (high - density).
• Frequencies: Frequency is a property of a wave (number of oscillations per second) and not a region.
• Pitches: Pitch is the perception of frequency (high or low) and not a region.
• Rarefactions: Rarefactions are regions in a sound wave where air molecules are spread out (low - density).

Answer:

D. rarefactions