sound will travel fastest in air at

a.) -5°c
b.) 0°c
c.) 10°c
d.) 15°c

Answer is the highest temperature, so D

Higher temperatures allow for sound to move faster, since the molecules vibrate faster, sound waves can travel more quickly. The speed of sound in room temperature air is 346 meters per second. This is faster than 331 meters per second, which is the speed of sound in air at freezing temperatures.

Neat little fact: This is also why in the winter when there is snow on the ground, it seems more peaceful and quite. The snow absorbs the sound waves and the temperature makes them not travel as fast, getting more quite as they go.