The correct answer is option 4: 1, 2, 3, 4, and 5.

Biogas is generated through a process called anaerobic digestion, in which organic materials are broken down by bacteria in the absence of oxygen. These organic materials, known as substrates, can come from various sources.

1. Animals wastes: Animal waste, such as cow dung, pig manure, and poultry litter, is a common substrate for biogas generation. These wastes contain high amounts of organic matter that can be easily digested by bacteria.

2. Crop residues: The leftover plant materials from agricultural activities, such as stalks, husks, and leaves, can also be used as a substrate for biogas generation. These crop residues are rich in organic content and can be effectively converted into biogas.

3. Aquatic plants: Certain aquatic plants, such as water hyacinths and seaweeds, have high levels of biomass and can be used as a substrate for biogas production. These plants are often abundant and can be harvested sustainably.

4. Night soil: Night soil refers to human excreta, including urine and feces. It can be a potential substrate for biogas generation,