The answer is B. The lithosphere is the uppermost layer. This word is derived from word sphere combined with the Greek word lithos meaning rock. The lithosphere is the solid outer section of earth which includes Earth's crust (the "skin" of rock on the outer layer of planet earth) as well as the underlying cool, dense and rigid part of the upper mantle.
The lithosphere extends from the surface of the earth to a depth of about 44 - 62 miles (70 - 100 km) . This relatively cool and rigid section of earth is believed to float on top of the warmer non rigid and partially melted material directly below.
