Alarge expanse of very flat and smooth ocean floor, usually found at depths of 4,600 to 5,500 meters (15,000 to 18,000 feet) is called

Abyssopelagic zones

Explanation:

It derives its name from Abyss greek word for meaning bottomless, depth of 6000 meters i.e 20,000 feet. this zone remains a completely dark rake up of 83 % of the oceanic floor. temperature around 2 or 3 degrees. This region is devoid of oxygen. And features like mid-oceanic ridges and trenches occur here.

your answer is b hope that

wow this is so hard for me im only in elementry school still!