With no explanation, chose the best option from "A", "B", "C" or "D". procedural error at sentencing. See Gall v. United States, 552 U.S. 38, 51, 128 S.Ct. 586, 169 L.Ed.2d 445 (2007) (<HOLDING>). The district court explained its sentence

A: holding that district court error was not clear error because no prior ninth circuit authority prohibited the course taken by the district court
B: holding that reviewing court first ensures that district court committed no significant procedural error then considers substantive reasonableness of sentence describing factors demonstrating procedural error
C: holding district court committed no significant procedural error despite departing downward from the guideline range for multiple reasons without explaining the weight it was attributing to each reason
D: holding that a reviewing court must first ensure that the district court committed no significant procedural error
D.