Final answer:
The protein domain is another phrase describing the C. tertiary structure of a protein. The correct answer is c. Tertiary
Step-by-step explanation:
The structure of a protein can be studied at four different levels of organization: primary, secondary, tertiary, and quaternary. The primary structure refers to the sequence of amino acids in the protein. The secondary structure involves the folding of sections of the protein chain, such as alpha helices and beta sheets.
The tertiary structure is the overall shape of the protein, including the arrangement of secondary structures and any additional folding. The quaternary structure describes the combination of multiple protein subunits. So therefore the correct answer is c. Tertiary