Which of the following is not a type of power source utilized in alternative fuel vehicles?

The correct answer is coal. In the context of alternative fuel vehicles, the focus is primarily on fuels that can be used to power vehicles with lower emissions than conventional gasoline or diesel. Biodiesel, methanol, and natural gas are all recognized types of alternative fuels.

Biodiesel, derived from vegetable oils or animal fats, offers a renewable option that can reduce greenhouse gas emissions compared to traditional diesel fuel. Methanol is another alternative fuel, which can be produced from a variety of renewable sources and can be used in fuel cells or internal combustion engines. Natural gas, being a cleaner-burning fossil fuel, emits fewer pollutants than gasoline or diesel and is used in a growing number of vehicles.

Coal, however, does not fit the category of alternative fuels for vehicles in a meaningful way. While coal can be used to produce electricity, which can then power electric vehicles, it is not used directly as a vehicle fuel. Moreover, coal combustion is associated with higher emissions of carbon dioxide and other pollutants compared to the other options listed. Thus, coal does not meet the criteria usually associated with alternative fuel vehicles.