The correct answer is: A. Animal wastes
Biogas is a renewable energy source that can be produced from organic materials such as animal wastes, crop residues, and aquatic plants. It is a mixture of methane, carbon dioxide, and other gases that can be used to generate electricity, heat, or fuel vehicles.
Animal wastes are a good source of biogas because they are high in organic matter. When animal wastes decompose, they produce methane, which is a greenhouse gas. However, methane can be captured and used as a renewable energy source.
Crop residues are another good source of biogas. Crop residues are the leftover parts of plants after they have been harvested. They include stalks, leaves, and cobs. Crop residues are high in carbohydrates, which can be converted into biogas.
Aquatic plants are also a good source of biogas. Aquatic plants are plants that grow in water. They include algae, seaweed, and water hyacinth. Aquatic plants are high in organic matter, which can be converted into biogas.
Forest residues are the leftover parts of trees after they have been harvested. They include branches, leaves, and stumps. Forest residues are high in cellulose, which can be converted into biogas.
However, animal wastes are the most common source of biogas because they are readily available and have a high energy content.