Answer: The answer is B: abyssal plains
Abyssal plain is the term that is used described as a flat expanse of ocean floor.
Explanation: Abyssal plains refer to featureless areas on earth which are flattest, huge and sediment-covered area of the deep ocean floor. Abyssal plain are found at depths between 3,000 metres (9,800 ft) and 6,000 metres (20,000 ft). Abyssal plains cover more than 50% of the earth surface.
