The correct answer is B) natural gas.
All of the following are examples of alternative energy sources except natural gas.
Biofuels, natural gas, solar power, and hydroelectricity are examples of alternative energy sources.
Natural gas is fossil fuel, not an altenative energy sources. There is plenty of natural gas reserves in the United States- Indeed it is exported to other countries such as Mexico.
Biofuels are produced by biomass, that is matter derived from animals and plants. Is a good source of alternative energy with solar energy and hydroelectricity, that help to take care of the environment.