Which statement describes the size of the inner planets?
O All the inner planets, except Mercury, are large.
O The inner planets are larger than the outer planets.
O All the inner planets are smaller than the outer planets.
O Mars is a large planet, while the other inner planets are small.

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.