Question

what does it mean when an element has been sequestered? it is turned into energy. it is released into the air. it is isolated in a stable form. it completely disappears.

Explanation:

When an element is sequestered, it means it is isolated in a stable form. This is a common concept in environmental sciences (e.g., carbon sequestration where carbon is stored in a stable reservoir like geological formations). Turning into energy is against conservation laws (mass - energy equivalence is a different concept). Releasing into air is the opposite of sequestration. Elements don't completely disappear as matter is conserved.

Answer:

It is isolated in a stable form.