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

The chemical reactions lab we did is typically called a "copper plating lab,  because the acid solution cleaned the pennies and made the copper look shinier;   the acid solution cleaned the paperclips and made them look like pennies;   &   the copper from the pennies was removed, and then added to the paperclips. 

The fuzzy edges of shadows are a result of  diffraction