How does sound travel through a medium?

a: particles vibrate parallel to the direction the sound travels

b: particles movie in a circular motion

c: sound does not move through a medium

d: particles vibrate perpendicular to the direction the sound travels

sound travel as a back-and-forth  vibration of the particles of it's medium

the gas collects in coils that then becomes a liquid that then flows through the coils inside the refrigerator

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )