Answer:
The abyssal plains
Step-by-step explanation:
The abyssal plains are the regions in the seafloor that are comparatively flat and extends upto hundreds of kilometer wide and a few thousands of kilometer in length. They are usually at a depth ranging from 3500 to 6000 m below the sea level.
The topography of these plains are relatively very smooth. The rate of accumulation of the sediments is very slow and they were assumed to be a stable environment that has undergone least changes. The slope of these abyssal plain is smaller than the continental shelf.