Seismic Waves Show a Sudden Increase at the Mohorovicic Discontinuity

Multiple Choice

Seismic waves show a sudden increase at the Mohorovicic discontinuity because the

A) mantle material is so much hotter than the crust.
B) composition of minerals on both sides of the layer is different.
C) mantle is so much thicker than the crustal layer.
D) mineral structure is different in this layer than in crustal rock.