Which of the following comparisons of fusion and fission is correct? a. both fission and fusion result in products that are heavier than the reactants. b. both fission and fusion create far more energy out of far less matter than combustion. c. both fission and fusion involve the combining of neutrons to form new atoms. d. neither fission nor fusion produce any radioactive material.

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.