A pollutant that is biodegradable is

1. Analyze the question The question asks which pollutant is biodegradable. Biodegradable means it can be broken down naturally by living organisms, mainly bacteria and fungi (decomposers), into simpler harmless substances.

2. Explain the concept

• Biodegradable pollutants are organic materials that microorganisms can decompose. Examples: sewage, food waste, paper, animal dung.
• Non-biodegradable pollutants cannot be broken down by microorganisms, or break down extremely slowly. Examples: plastics, heavy metals, glass, DDT.

3. Go through the options

• A. Crude oil: It is a complex mixture of hydrocarbons. A few microbes can degrade it, but very slowly, and it persists in the environment (think of Niger Delta spills lasting for years). It is generally treated as non-biodegradable in the exam context.
• B. Heavy metals: Lead, mercury, cadmium and similar metals are elements. They cannot be broken down at all and accumulate in food chains. Non-biodegradable.
• C. Cellophane: It is a plastic-like film. Although technically made from cellulose, in JAMB-level questions it is grouped with packaging materials that resist decay. It is not the intended answer.
• D. Sewage: It is made of organic waste (human and animal excreta). Bacteria readily decompose it, so it is biodegradable. It is still a pollutant because, in large amounts, it contaminates water and spreads disease (cholera, typhoid).

4. Answer The biodegradable pollutant is sewage, which is option D.

5. Exam tip Ask yourself: "Can bacteria feed on it?" If it comes from living things (sewage, food scraps, paper, dung), it is biodegradable. If it is a metal, plastic, glass or synthetic chemical, it is usually non-biodegradable.