Which among the following is the main source of “Synthetic Fuel”?

Q. Which among the following is the main source of “Synthetic Fuel”?
Answer: Coal
Notes: Synthetic fuel is a liquid or gaseous fuel (which is obtained from a mixture of carbon monoxide and hydrogen) which was formed by coal or biomass or by reforming of natural gas. Some of the conversion methods are Fischer–Tropsch conversion, methanol to gasoline conversion, direct coal liquefaction.