Through which of the following will a sound wave travel the fastest?
a. water
b. air
c. outer space
d. a wall
the answer is d, a wall.

D. A wall

Explanation:

Sound waves consist of oscillations of the particles in the medium in which the wave is travelling through. They are longitudinal waves, which means that the particles in the medium oscillate back and forth along the direction of motion of the wave, forming alternate regions of higher density (compressions) and lower density (rarefactions).

The speed of the sound waves depend on the properties of the medium. In particular, the more packed the particles are in the medium, the faster the sound waves are, because the vibrations between the particles are transmitted more efficiently/faster (because there is less separation between the particles). Since solids have higher density than liquids, and liquids have higher density than gases, this means that sound wave travel the fastest in solids, so the answer is D. A wall.

Also note that sound wave cannot travel in outer space, since they cannot travel in a vacuum (because there are no particles that can trasmit the vibrations).

i believe the answer is a