What does “biodegradable” refer to?

"Biodegradable" refers to materials that can be broken down by natural processes, typically by microorganisms like bacteria and fungi. This process involves the decomposition of organic matter, which results in the conversion of the material into natural substances such as water, carbon dioxide, and biomass, thus minimizing environmental impact.

Choosing this option accurately reflects the essential characteristic of biodegradable materials: their ability to return to the ecosystem without leaving toxins or harmful residues. This is crucial for sustainability, as it promotes recycling of nutrients and reduction of waste in landfills.

In contrast, the other options describe aspects that do not align with the concept of biodegradability. Materials that cannot be broken down would contribute to persistent waste issues, while those that release harmful substances are typically considered pollutants rather than environmentally friendly materials. Lastly, materials made solely from plastic do not inherently indicate biodegradability, as many plastics are non-biodegradable and can persist in the environment for hundreds of years.