The age of the ocean floor is greatest in subduction zones or
a. closest to deep-ocean trenchesb) farthest from the mid-ocean ridgesc) closest to the central valley of the mid-ocean ridged) farthest from deep-ocean trenches

The correct answer is - farthest from the mid-ocean ridges.

The mid-ocean ridges are the places were the new crust is forming, in the form of a new ocean floor. This is due to the divergent plate boundaries on those places, so the magma manages to easily penetrate upwards and create new crust. Because of the movement of the plates away from the mid-ocean ridge, the crust is easily sorted out by age. The one that is on the mid-ocean ridge is the youngest, and the farther you move from it the crust is older and older, thus the crust is older at the places that are the farthest away from the mid-ocean ridge. These places coincide with the subduction zones where the crust is getting down into the mantle.