Which of the following properties of an unknown substance would allow it to be classified as a pure substance ? A- can be dissolved into a solution
B- has a definite composition throughout
C- combines easily with other substances
D- is made of a single element or compound

How is electrolysis most commonly used to produce an energy source? a - splitting water molecules produces oxygen, which organisms breathe to fuel their bodies. b - splitting water molecules produces hydrogen gas, which is used to power machines through hydrogen fuel cells. c - splitting carbon dioxide molecules produces coal, a form of carbon that can be burned to produce heat. d - splitting carbon dioxide molecules produces natural gas, which can be burned to generate electricity in power plants.