Concept:Substances that can be decomposed by living organisms are called biodegradable.
Explanation:Biodegradable substances are broken down into simpler compounds by the action of microorganisms like bacteria, fungi, and earthworms.
These materials are typically organic in nature and return nutrients and humus to the soil, thereby supporting the biogeochemical cycles of the ecosystem.
Common examples include vegetable peels, paper, wood, and animal waste.
In contrast, non-biodegradable substances cannot be decomposed by biological processes.
They remain in the environment for a very long time and cause pollution.
Plastics, glass, and heavy metals are typical non-biodegradable materials.
The terms hard material and soft material indicate physical properties like mechanical strength and resistance to scratching; they are not related to biodegradation.
Composting is a controlled biological process that accelerates the decomposition of biodegradable waste into humus, which acts as a natural fertilizer.
Thus, the correct option is Biodegradable.
Answer:D. Biodegradable