Which energy source is considered a biofuel?

C. Biogas is considered a biofuel because it is produced through the anaerobic digestion of organic materials such as agricultural waste, animal manure, and food scraps. This process converts the organic material into methane, which can then be used as a renewable energy source. Biogas not only helps in reducing waste but also contributes to a reduction in greenhouse gas emissions when used instead of fossil fuels.

In contrast, natural gas and coal are fossil fuels derived from ancient biological materials, but they are not classified as biofuels since they are not produced from current biological processes. Nuclear energy, on the other hand, relies on nuclear fission rather than biological material, making it unrelated to the category of biofuels. Hence, biogas stands out as the renewable and environmentally-friendly energy source among the options provided.