There are four levels of protein structure. Which level includes the

Correct answer: B) Secondary structure.
The secondary structure of a protein refers to the local arrangements of amino acids, including the coils of the α helix and the folds of the β pleated sheets. These structures are stabilized by hydrogen bonds between amino acids and are a result of the interactions between the amino acids in the protein sequence.

Here's a brief overview of the four levels of protein structure:
Primary structure: the sequence of amino acids in a protein.
Secondary structure: local arrangements of amino acids, such as α helices and β pleated sheets.
Tertiary structure: the overall 3D shape of a single protein molecule.
Quaternary structure: the arrangement of multiple polypeptide chains in a protein.