With no explanation, chose the best option from "A", "B", "C" or "D". the district court’s instructions. See Bennett, 368 F.3d at 1351. Simply put, Overton has not met his burden to show that there is “a reasonable probability ... that, but for the remarks,” the outcome of his trial would be different, and thus, he has not shown prejudice to his substantial rights. See Hall, 47 F.3d at 1098. Accordingly, we affirm. AFFIRMED. 1 . We deny Overton’s motion to file a supplemental brief to argue, for the first time, that Blakely v. Washington, 542 U.S. 296, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004), applies to his case. It is well-established that we will not consider such arguments when they are not raised in the initial brief. See United States v. Duncan, 400 F.3d 1297, 1299 n. 1 (11th Cir.2005) (citing United States v. Levy, 379 F.3d 1241 (11th Cir.2004) (<HOLDING>); United States v. Nealy, 232 F.3d 825, 830

A: holding that appellant waived issue by failing to raise it in opening brief
B: holding party failing to adequately brief complaint waived issue on appeal
C: holding that party waived argument by failing to brief it on appeal
D: holding that defendant waived his blakely claim as issue on appeal by failing to raise it in his initial brief
D.