In the Mississippi River Delta in South Louisiana Shallow Subsurface

In the Mississippi River delta in south Louisiana shallow subsurface imaging of the sediments reveal buried channels beneath delta sediments that are less than 10,000 years old that extend offshore past the modern continental shelf. What is a simple explanation for these buried channels?

A) The river must have been bigger in the past, cutting a channel clear to the edge of the shelf below sea level.
B) They represent channels of the Mississippi river delta when sea level was lower, during the ice age.
C) Turbidity currents cut a submarine canyon on the shelf before the delta buried them.
D) They represent giant flood events before the delta was formed and before the river formed.