Which relatively flat feature of the ocean floor is in the open ocean and borders the continental shelf? abyssal plain mid-ocean ridge continental slope deep-ocean trench

The answer would be:

Abyssal plain

Here is more about this feature:

Abyssal plains are flat wide areas of the ocean floor. You can find these features in between a continental rise and a mid-oceanic ridge. These plains are covered in sediment and are found deep down the ocean floor. They are typically featureless, but they sometimes have hills as well, and the hills are called Abyssal hills.

1a) 12,20,28,36

1b) 29,37,46,56

1c)3,-7,-17,-27

Step-by-step explanation: