Choose the correct IUPAC nomenclature for the given structure below: A$.5-$ Cyano$-N-$ethyl$-$N$-$methylpentanamide B$.2-$Cyano$-$N$-$ethyl$-$N$-$methyl$-$hexanamide C$.3-$Cyano$-1-$ethy$-2-$keto$-1-$methyl$-$hexane D$.2-$Cyano$-$N$-$ethyl$-$N$-$methylpentanamide