Identify the statement true of isostasy. Choose one: A. Isostasy is reached when the lithosphere is sinking into the asthenosphere. B. Isostasy is reached with the lithosphere is actively mixing with the asthenosphere. C. Isostasy is reached when the lithosphere is buoyantly rising within the asthenosphere. D. Isostasy is reached with the lithosphere is neither sinking nor rising relative to the asthenosphere.

Isostasy refers to the principle of buoyancy in which an object immersed in a fluid is buoyed with a force equal to the weight of the displaced fluid. This means that a state of gravitational equilibrium has been reached between the lithosphere and the asthenosphere such that the lithosphere "floats" at an elevation that depends on its thickness and density. In Isostasy, the lithosphere is neither rising or sinking, and therefore in any region undergoing a change in vertical position, isostasy can provide a 'view' of the processes that are happening in such regions.