In a skeletal formula of a fatty acid, what do the unlabeled sharp corners (vertices) along the zigzag chain represent?

• A. Carbon atoms of the hydrocarbon chain
• B. Oxygen atoms in the carboxyl group
• C. Nitrogen atoms involved in amide bonds
• D. Points where implicit hydrogen atoms are attached and each vertex represents a carbon atom in the chain; hydrogens are not drawn explicitly in the skeletal representation

Answer: (A)