Where the crust is being pulled apart due to the motion of tectonic plates
d.mantle
b. plate tectonics
c. transform plate
a. Mid ocean ridges

The overlying oceanic crust to the ocean floor where it creates a chain of volcanic island known as
a. mountain
b. volcano
island arc
c. earthquake

The middle layer, more dense than the crust, compose of the upper mantle, the lithosphere, and the lower mantle.
d. mantle
a. core
c. crust
b. plate tectonics