In environmental science, which of the following everyday materials is considered biodegradable by natural decomposers?

Introduction / Context:
Biodegradability is a key concept in environmental science and waste management. A biodegradable material can be broken down by natural organisms such as bacteria and fungi into simpler substances that re enter the environment without long term pollution. Non biodegradable materials persist for a very long time and may accumulate, causing serious environmental problems. This question asks you to identify which common material among the options is biodegradable, based on its origin and chemical nature.

Given Data / Assumptions:
- Options include iron nails, DDT, silver foil, and leather bags.
- Biodegradable materials are usually organic in nature and can be decomposed by microbes.
- Non biodegradable materials typically include many metals and synthetic chemicals that resist natural breakdown.
- The question assumes basic awareness of organic versus inorganic and synthetic substances.

Concept / Approach:
Biodegradable materials are often derived from living organisms and consist of organic compounds that microbes can use as food. Leather is produced from animal hides, which are made primarily of proteins and other organic components. Even though leather is treated and tanned, it remains an organic material that can eventually be decomposed by microorganisms. In contrast, iron nails and silver foil are metals, which do not undergo biodegradation. They may corrode or oxidise but are not broken down by living organisms into harmless natural products. DDT is a synthetic pesticide that is well known for being persistent and non biodegradable, accumulating in food chains and causing long term environmental harm.

Step-by-Step Solution:
1. Recall that biodegradable materials are those that can be broken down by living organisms into simpler, non harmful substances. 2. Identify the nature of iron nails: they are metallic and can rust, but rusting is a chemical process, not biodegradation. 3. Recognise that silver foil is also metallic and does not serve as a food source for decomposer organisms. 4. Recall that DDT is a synthetic insecticide famous for its persistence and lack of biodegradability. 5. Note that leather bags are made from processed animal skin, an organic material that decomposers can eventually break down, making them biodegradable.

Verification / Alternative check:
Environmental studies materials and school textbooks commonly list examples of biodegradable and non biodegradable items. Organic waste such as food scraps, paper, cotton, and leather is placed under biodegradable waste. Metals, plastics, and many synthetic chemicals like DDT are listed as non biodegradable. If you check case studies on pesticide pollution, DDT is always highlighted as a persistent organic pollutant that does not break down easily. These consistent examples verify that leather, despite processing, is comparatively biodegradable, while the other listed items are not.

Why Other Options Are Wrong:
Iron nails: They undergo rusting due to oxidation but are not decomposed by microorganisms and are therefore not considered biodegradable in the usual environmental sense.
DDT: This pesticide is known for being highly persistent and non biodegradable, causing bioaccumulation and biomagnification in food chains.
Silver foil: Silver is a metal that does not decompose through biological processes and remains in the environment for a very long time.

Common Pitfalls:
A common mistake is to confuse any form of breakdown with biodegradation. Rusting of metals is often misinterpreted as biodegradation, but it is purely a chemical reaction with oxygen and moisture. Another pitfall is to consider synthetic chemicals like DDT as biodegradable simply because they are organic compounds by structure. However, their molecular stability and toxicity prevent common decomposers from breaking them down easily. To avoid these errors, remember that biodegradable materials are usually natural, less chemically stable, and can serve as a substrate for microorganisms.

Final Answer:
Among the options, leather bags are biodegradable because they are made from animal skin that can be decomposed by natural microorganisms.