Discussion Topic Chemical reactions constantly take place all around us—and even inside us. Many reactions occur naturally. But sometimes humans cause the reactions. Do you think you could go a week without causing any chemical reactions? Explain why or why not, providing examples where appropriate. Do not count reactions that take place inside your body.

15. which of the following is not human-caused groundwater pollution? a. water in an aquifer dissolves elements such as arsenic and mercury from surrounding rock. b. water in an aquifer is contaminated by leachate that seeps into the ground from a landfill. c. water in an aquifer becomes polluted with chemicals used in hydraulic fracturing, or fracking. d. water in an aquifer absorbs harmful bacteria from the drainage field of a septic tank.