With no explanation, chose the best option from "A", "B", "C" or "D". One of the grounds was that counsel failed to challenge the constitutionality of convictions the court purportedly used to enhance his sentence under 21 U.S.C. § 851. The court referred the motion to a magistrate judge, who recommended that the motion be denied. The court followed the recommendation and denied relief. The court also denied petitioner’s application for a certificate of appealability (“COA”). We thereafter issued a COA for this issue: Whether the district court erred by failing to address [petitioner’s] claim that he received ineffective assistance of counsel based on counsel’s failure to challenge the district court’s alleged use of several invalid prior convictions to enhance his sentence in the instant case. See Clisby v. Jones, 960 F.2d 925, 936 (11th Cir.1992) (<HOLDING>). The district court did err. In disposing of

A: holding that habeas claim not included in petition and never raised by petitioner before the district court as basis for habeas relief is procedurally defaulted
B: holding that infirmities in state habeas proceedings do not constitute grounds for federal habeas relief
C: holding that insufficiency of indictment is not a basis for habeas relief
D: holding that the district court must resolve all claims for relief raised in a habeas petition regardless of whether habeas relief is granted or denied
D.