Abyssal plains are very flat features that form when
a. volcanoes spread lava on the ocean bottom.
b. turbidity currents deposit sediments on the ocean floor.
c. ocean waters flood plains on land.
d. plates diverge on the ocean floor, causing seafloor spreading.

b. turbidity currents deposit sediments on the ocean floor.

Abyssal plains are flat land forms found in the lower depth of the oceans. The flat seafloor forms by the deposition of the thin blanket of muddy sediments, that sinks at the bottom of the ocean. These sediments covers the volcanic rocks of the oceanic crusts. These muddy sediments are brought below the sea floor by the turbid water currents.

not too sure thinking it will always be directed towards the centre of the earth. could be wrong not sure

close lines strong magnet less close weaker