When the brain, spinal cord and nerves of the body communicate with each other, it represents the level of organization.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.