With no explanation, chose the best option from "A", "B", "C" or "D". of the structure extended approximately four to five feet above the waterline, but that the sill had been completely submerged at all but the lowest water levels since approximately 1976. This is supported by the testimony of Emile Shilling, the operations project manage er for the Corps with authority over this area of the Mississippi River. Shilling also testified that despite the erosion of the levees and the fact that the sill no longer extends across the entire cut, the structure still serves its purpose to reduce silt buildup in the South Pass, thereby reducing the need for maintenance dredging. Based on this evidence, the district court rejected the argument that the United States was negligent for failing to maintain the sill in its original condition as the sill’ 5th Cir.1987) (<HOLDING>); Sheridan Transp. Co. v. United States, 834

A: recognizing a discretionary function exception to that waiver
B: holding that decision to operate lighthouse is discretionary decision while failure to maintain lighthouse is not within discretionary function exception
C: holding that the discretionary function exception may apply in the absence of a conscious decision 
D: holding that decision to establish recreational swimming area was discretionary but failure to replace buoy secured by an anchor that injured a swimmer was not within discretionary function exception
D.