Answer: a. Primary level.
Explanation:
The primary level is characterized by the sequence of aminoacids of the protein, aminoacids have a carboxyl and an amino group bonded to a carbon atom, and are held together by peptide bonds between the carboxyl end of an aminoacid and the amino end of the next one, making an aminoacid chain.
Secondary, tertiary and quaternary levels determine the shape and thus the function of the protein according to different forces, hydrogen bonds take part in it bending the chain in different ways.
