Answer:
(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.