The age of the ocean floor is greatest in subduction zones or farthest from the mid-ocean ridges farthest from deep-ocean trenches closest to deep-ocean trenches closest to the central valley of the mid-ocean ridge

The correct answer is "closest to deep-ocean trenches".

Explanation:

Subduction zones are regions of the Earth at which a tectonic plate moved beneath another due to the presence of high gravitational potential energy into the mantle. The age of the ocean floor is greatest in subduction zones because the process of gravitational sink takes place where oceanic crust and lithosphere are old and thick. The ocean floor is also old at regions closest to deep-ocean trenches, the locations with the deepest zones on Earth, because these places also suffer from gravitational sink causing earthquakes and the formation of sea floor volcanoes.