Final answer:
The Pacific Ocean is the ocean basin with the most subduction zones, making it the most tectonically active.
Step-by-step explanation:
The Pacific ocean basin is rimmed by the most subduction zones. Subduction zones are areas where one tectonic plate is forced beneath another, leading to the recycling of the oceanic crust into the mantle. These zones often correspond with ocean trenches such as the Japan trench, and are significant in the context of plate tectonics and the creation and destruction of crust. The Pacific Ocean, surrounded by the 'Ring of Fire', has the most subduction zones, with numerous examples like the Japan trench, the Peru-Chile trench, and the Marianas trench, making it the most tectonically active ocean basin.