Why does the magma in the upper mantle sink? please respond fast :)

As the denser structural plate subducts, or sinks underneath, or the less-dense tectonic plate, hot shake from underneath can interfere into the cooler plate over. In this case, water overlying the subducting seafloor would lower the dissolving temperature of the mantle, creating magma that rises to the surface

:)

the answer is b. hope this !