Explanation:

The correct answer is option 'D' - Biofuel. Biofuel is a type of fuel that is derived from living and dead biological organisms. It is a renewable source of energy as it is made from organic matter which can be replenished.

Here is a detailed explanation of biofuel:

Definition of Biofuel:
Biofuel is a type of fuel that is produced from organic matter, such as plants, algae, and even animal waste. It is considered a renewable source of energy because the organic matter used to make biofuel can be grown and harvested repeatedly.

Types of Biofuel:
There are several types of biofuels, including:

1. Ethanol: Ethanol is a biofuel that is made from crops such as corn, sugarcane, and wheat. These crops undergo a fermentation process to convert their sugars into ethanol. Ethanol can be used as a fuel additive or as a complete replacement for gasoline in vehicles.

2. Biodiesel: Biodiesel is a biofuel that is made from vegetable oils, animal fats, or recycled cooking grease. These feedstocks undergo a chemical process called transesterification to convert them into biodiesel. Biodiesel can be used as a replacement for diesel fuel in vehicles.

3. Biogas: Biogas is a biofuel that is produced through the anaerobic digestion of organic matter, such as agricultural waste, food waste, and sewage. The organic matter is broken down by bacteria in the absence of oxygen, producing a mixture of methane and carbon dioxide. Biogas can be used as a fuel for heating, electricity generation, and even as a vehicle fuel.

Advantages of Biofuel:
- Renewable: Biofuel is derived from organic matter, which can be grown and harvested repeatedly.
- Reduced greenhouse gas emissions: Biofuel produces fewer greenhouse gas emissions compared to fossil fuels, helping to mitigate climate change.
- Energy independence: Biofuel can be produced locally, reducing dependence on foreign oil imports.
- Job creation: The biofuel industry can create jobs in agriculture, manufacturing, and research.

Conclusion:
Biofuel is an important source of renewable energy that is derived from living and dead biological organisms. It can be produced from a variety of feedstocks and has several advantages over fossil fuels. By using biofuel, we can reduce greenhouse gas emissions, promote energy independence, and create jobs in the biofuel industry.