Final answer:
The Mississippi Delta is indeed losing area due to the fact that the sediment supply is insufficient to combat the rates of erosion and subsidence, thus confirming the statement as true. The correct answer is option a.
Step-by-step explanation:
The statement that the Mississippi Delta is losing area because the supply of sediment is less than the rates of delta erosion and subsidence is true. Deltas form where rivers deposit sediment as they enter another body of water, like an ocean or a lake. When a river like the Mississippi carries a high silt content and discharges into an ocean with minimal current and wave action, it builds a delta with sand and mud as the silt settles. However, factors such as human intervention through the construction of levees, dams, and channels can reduce the supply of sediment the river carries. Furthermore, natural processes like erosion and subsidence contribute to the loss of delta land. In the case of the Mississippi Delta, the rates of erosion and subsidence have exceeded the amount of sediment supplied, leading to a net loss in the delta area.