The part of the diagram labeled as "Ridge" represents a mid-ocean ridge, where two tectonic plates move away from each other. The part of the diagram labeled as "Trench" marks an ocean trench, a location beneath which one plate plunges under another.

According to this diagram, convection currents begin to move beneath mid-ocean ridges and begin to move beneath trenches.
A.
downward; upward
B.
downward; downward
C.
upward; downward
D.
upward; upward