A)the amino acid residues that have the greatest degree of rotational freedom B)the sterically allowed rotational angles between R groups and a-carbons in a peptide C)the sterically allowed rotational angles between Cα and the amide nitrogen (Cα-N),as well as between Cα and the amide carbonyl carbon (Cα-CO) D)the sterically allowed rotational angles about the amide nitrogen (NH)and CO