Question

a guitar string is plucked. what best describes the formation and transmission of the sound wave?
the string vibrates the surrounding air, which produces a transverse wave.
the string vibrates the surrounding air, which produces a longitudinal wave.
the string produces a longitudinal wave that travels without a medium.
the string produces a transverse wave that travels without a medium.

Explanation:

Sound waves are longitudinal waves. When a guitar string is plucked, it vibrates the surrounding air. Sound waves require a medium (like air) to travel. Transverse waves have particle motion perpendicular to wave direction (e.g., light in vacuum - but sound isn't like that). Longitudinal waves have particle motion parallel to wave direction (how sound travels in air). So the plucked string vibrating air produces a longitudinal wave (needs medium - air here).

Answer:

The string vibrates the surrounding air, which produces a longitudinal wave.