With no explanation, chose the best option from "A", "B", "C" or "D". to resentencing. In Gall, 552 U.S. at 40, 128 S.Ct. 586, the Supreme Court explained that a district court must begin the sentencing process by correctly calculating the appropriate guidelines range. The error in this case therefore appears to be plain. Regarding whether the error affected Varnado’s substantial rights, we are cognizant of the fact that the district court granted Varnado a variance/departure and sentenced Varnado to the low end of the improperly calculated guideline range (within a window of 63 to 78 months). It is reasonable to presume that the district court might have imposed a lower sentence had it been aware of the correct guidelines range. We therefore hold that Varnado is entitled to resentencing. See United States v. McCrary, 887 F.2d 485, 489 (4th Cir.1989) (<HOLDING>). Because the district court must resentence

A: holding sentence within properly calculated advisory guidelines range is presumptively reasonable
B: holding statutory error harmless where district court imposed the highest available sentence under guidelines range and considered sentencing to the statutory maximum
C: holding that defendant should be resentenced where district court imposed a sentence under an erroneously calculated guidelines range  even where the sentence imposed fell within the correct range
D: holding statutory booker error was not harmless where district court imposed sentence in middle of guidelines range and there were no statements in the record reflecting that the court would have imposed the same or greater sentence under advisory guidelines
C.