Correct Answer:
A. Coal gas
The mixture of hydrogen, methane, and carbon monoxide is commonly known as Coal gas. This combustible gaseous fuel was historically produced from coal through a process called coal gasification and was widely used for lighting and heating before the advent of natural gas.
- CNG (Compressed Natural Gas) is primarily composed of methane and is used as a fuel for vehicles.
- Biogas is produced from the anaerobic digestion of organic matter and consists mainly of methane and carbon dioxide.
- Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane.