Final answer:
A beta-sheet is part of a protein's secondary structure, which is stabilized by hydrogen bonds and is a precursor to the tertiary structure associated with the protein's biological function.
Step-by-step explanation:
A beta-sheet exemplifies the secondary structure of a protein. The primary structure refers to the sequence of amino acids, whereas the secondary structure includes configurations such as alpha helices and beta sheets, which are maintained by hydrogen bonds between the amino acids. These secondary structures can further interact and fold to form the tertiary structure, which is the overall three-dimensional shape of the protein. Finally, the quaternary structure is the arrangement of multiple tertiary structures or subunits, as is the case with proteins like hemoglobin. The biological function of a protein is most often associated with its tertiary structure, where its complex folding allows it to perform specific functions within the body.
Therefore, the beta-sheet is part of the secondary structure, Option B.