15. Which of the following is aδ-lactone? (A)(B)(C)(D)(E)

6. Planarity of the peptide bond means that rotation is allowed about the bond linking ___________the and the carbon of the peptide bond, and also about the bond linking the___________ to the adjacent α-carbon. (A) a-carbon, carbony1 carbon (B) B-carbon, carbonyl carbon (C) carbonyl carbon, nitrogen of the peptide bond (D) a-carbon, nitrogen of the peptide bond (E) none are true