The secondary structure of a protein refers to the .a. three-dimensional folded structure of the protein. b. configuration of the folded protein when bound to other proteins. c. linear assembly of amino acids into a chain. d. twisting of the amino acid chain into a corkscrew-like shape or into a zigzag folding pattern. e. None of the above answer choices is correct.

(A.) three dimensional folded structure of the protein

Explanation:

The secondary structure of a protein is a regular structure built from interactions between neighboring amino acids as the polypeptide starts to fold or coil into its functional three-dimensional shape.

The two kinds of secondary structures arising from this polypeptide 'flexing' are either the  α-helix and β-pleated structures, all of which are vital to globular and fibrous proteins.