Sound travels from a phone speaker to the ear of the person listening to the call. Sound waves are modeled by the image below. 1) What do the dots in the image represent?
2) How do sound waves travel through air to a person's ear?

Which of these is an example of land degradation? a. containers designed to store pollutants leak. b. fertilizers provide too many nutrients to crops. c. garbage is buried so the land can be reclaimed later. d. a drought kills all the plants in an area, leaving bare land