Answer c is correct.. the steps are as follows
1. the facultative anaerobic microbes degrade the complex polymers to simple monomers by enzymatic action.
2. 2nd stage , monomers are converted into organic acids by microbial action and finally converted to acetic acid.
3. in 3rd stage, acetic acid is oxidized into methane by activity of anaerobic methanogenic bacteria.

The correct answer is option 'C', which states that the production of biogas through the anaerobic breakdown of biomass of agricultural waste by methanogenic bacteria is a three-step process. Let's understand each step in detail:

1. Hydrolysis:
- The first step in the production of biogas is hydrolysis, which involves the breakdown of complex organic compounds into simpler molecules.
- In this step, enzymes secreted by bacteria break down large molecules such as carbohydrates, proteins, and lipids present in the biomass into smaller molecules like sugars, amino acids, and fatty acids.
- The hydrolysis process occurs in the presence of water and is facilitated by a variety of bacteria and fungi.

2. Acidogenesis:
- After hydrolysis, the second step in the process is acidogenesis, which involves the conversion of the simpler molecules formed in the hydrolysis step into volatile fatty acids (VFAs) and alcohols.
- Various acidogenic bacteria are responsible for this conversion, and they produce VFAs such as acetic acid, propionic acid, and butyric acid, as well as alcohols like ethanol and methanol.
- Acidogenesis is an essential step as it provides the necessary precursors for the next step, methanogenesis.

3. Methanogenesis:
- The final step in the production of biogas is methanogenesis, where methanogenic bacteria convert the VFAs and alcohols produced in the acidogenesis step into methane gas (CH4) and carbon dioxide (CO2).
- Methanogenic bacteria are strict anaerobes, meaning they can only survive and function in the absence of oxygen.
- These bacteria use the VFAs and alcohols as substrates and produce methane gas through a series of metabolic reactions.
- The methane gas produced is the main component of biogas, along with carbon dioxide and small amounts of other gases like hydrogen sulfide and trace elements.

In conclusion, the production of biogas through the anaerobic breakdown of biomass of agricultural waste by methanogenic bacteria is a three-step process involving hydrolysis, acidogenesis, and methanogenesis. Each step is crucial for the overall production of biogas and involves the action of specific bacteria and enzymes.