Why is the force of gravity greater on Earth's surface than on Pluto's surface? O A. Earth is closer to the sun than Pluto is. O B. Earth has only one moon, while Pluto has three. C. Earth has a heavy atmosphere and Pluto does not. O D. Earth is more massive than Pluto.

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.