The build up of a substance in the body of a living thing

• A. Bioaccumulation
• B. Bioethanol
• C. Biogas
• D. Biomagnification

Answer: (A)

The concept being tested is the buildup of a substance inside a living organism over time. When a pollutant is continually taken up from the environment and not fully broken down or excreted, it accumulates in the body's tissues. That ongoing accumulation within an individual organism is bioaccumulation.

Think of it like a sponge soaking up a contaminant from water and holding onto it; even if the water’s concentration stays the same, the sponge’s internal concentration increases over time. This can happen with pesticides or heavy metals in aquatic organisms, for example.

This differs from biomagnification, which is about how the concentration of a substance increases as you move up through the food chain, from prey to predator, due to multiple transfers and processing across trophic levels.

The other options aren’t about accumulation in a living body: bioethanol is fuel produced by fermenting sugars, and biogas is methane-rich gas produced by anaerobic digestion.