Sound waves are longitudinal mechanical waves

Steps:

• Recall that sound travels through a medium by compressing and rarefying particles.
• Identify wave type: oscillations parallel to energy propagation define longitudinal waves.
• Eliminate electromagnetic options, as sound requires a medium.
• Confirm C matches the parallel oscillation description.

Why C is correct:

• By definition, longitudinal waves like sound involve particle displacement parallel to the wave's direction of travel, as per the wave propagation model.

Why the others are wrong:

• A: Sound is mechanical, not electromagnetic.
• B: Sound is not transverse; electromagnetic waves like light are.
• D: Perpendicular oscillation describes transverse waves, not sound.

Final answer: C