Why Is a Bird-Foot Delta Like That of the Present-Day

Multiple Choice

Why is a bird-foot delta like that of the present-day Mississippi below New Orleans likely to change naturally toward one with the shape of an equilateral triangle like the upper-case Greek letter delta (̇Δ) ?

A) Increased sediment loads since the mid-19th century have caused the major distributaries to be filled with sand.
B) Present-day distributaries have higher gradients than potential new ones.
C) Potential, new, distributary channels have higher gradients, causing downcutting of the existing channels.
D) Potential, new, major distributary channels have steeper gradients than existing channels.