What is the characteristic of sequestered manganese?

Sequestered manganese is characterized by its solubility in certain conditions, which is a key feature when considering its role in environmental and biological systems. Sequestration typically refers to the process by which a substance is isolated or separated from its surroundings, often involving the formation of complexes that keep it dissolved in solution.

In the case of manganese, when it is sequestered, it is often in the form of manganese complexes that allow it to remain soluble in water rather than precipitating out as a solid. This solubility is important in various applications, such as in water treatment processes where manganese needs to be removed or managed effectively, or in biological systems where manganese acts as an essential micronutrient without forming harmful precipitates.

The other characteristics mentioned, such as volatility and combustibility, do not accurately describe sequestered manganese. It is not a volatile substance; it does not readily vaporize at room temperature. Similarly, it is not combustible, meaning it does not ignite or burn under standard conditions. Insoluble forms of manganese would not be considered sequestered, as they would not exist in a dissolved state. Hence, the solubility feature of sequestered manganese distinguishes it and makes it the correct answer.