What must happen to uranium before it can be used as a fuel source?
A. Stable U-235 must be enriched with 3% radioactive U-238.
B. Stable U-238 must be enriched with 3% radioactive U-235.
C. No changes are necessary.
D. Unstable U-235 must be enriched with 5% U-238 to stabilize it.

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.