Sound · parallel · mechanical · not a vacuum · needs a medium · compressions and rarefaction what type of wave is being described? a) compaction b) electromagnetic c) longitudinal d) transverse

It is a longitudinal wave. In a longitudinal wave the particles of the medium vibrate in a direction parallel to the direction of energy transport. Sound waves are mechanical waves as well as longitudinal waves that require a medium. They do not travel through a vacuum.

the answer is neither ball has a charge.

because if they were both positively charged, they will repel each other.

if they were positively and negatively charged, they will seek.

b.a device that inputs heat into a cool object