Microbial fuel cells are considered a source of sustainable energy. Why? 1. They use living organisms as catalysts to generate electricity from certain substrates. 2. They use a variety of inorganic materials as substrates. 3. They can be installed in waste water treatment plants to cleanse water and produce electricity. Which of the statements given above is/are correct?

Statement 1 is correct. Microbial fuel cells (MFCs) use electroactive microorganisms (living organisms) as biocatalysts to break down organic or inorganic substrates and generate electrons, which are then converted into electricity. Statement 2 is incorrect or at least not entirely accurate in the context of their primary sustainable application. While some MFCs can utilize certain inorganic compounds, their most significant sustainable application often involves the breakdown of organic matter (e.g., in wastewater). The phrase "a variety of inorganic materials" is an overstatement and not their defining characteristic for sustainability compared to organic waste. Statement 3 is correct. A key advantage and sustainable application of MFCs is their ability to treat wastewater by breaking down pollutants (cleansing water) while simultaneously producing electricity. This dual benefit makes them highly sustainable, as they reduce energy consumption in wastewater treatment and generate renewable energy. Therefore, statements 1 and 3 are correct, making option C the right answer.