Which of the following is a fossil fuel?

The term fossil fuel refers to energy sources that come from the remains of ancient plants and animals, buried and subjected to heat and pressure over millions of years. These fuels are primarily composed of carbon and include materials like coal, oil, and natural gas.

Among the options given:

• Gneiss is a type of metamorphic rock formed from other rocks like granite or sedimentary rock through heat and pressure. It is not a fossil fuel.
• Granite is an igneous rock that forms from the cooling and solidification of magma beneath the Earth’s surface. It is not a fossil fuel.
• Lignite is a type of coal, which is a fossil fuel. It is often referred to as brown coal and is used primarily as a fuel for steam-electric power generation.
• Mica is a group of minerals that can split into thin, tough sheets. It is not a fossil fuel.

Therefore, the correct answer is Lignite because it belongs to the category of fossil fuels. Lignite is formed from the remains of plants that lived millions of years ago, which makes it a source of stored energy that can be burned for heat and power.