[A] The process where the upper continental crust subducts under an oceanic crust.

[B] The detachment and sinking of the dense lowermost lithosphere (including the mantle lithosphere and lower crust) from the tectonic plate, allowing the underlying asthenosphere to rise and replace it.

[C] The subduction of oceanic lithosphere beneath a continental plate leading to volcanic arc formation.

[D] The lateral sliding of tectonic plates past each other along transform faults causing earthquakes.