The correct answer is a) proteins.
Proteins are macromolecules that are made up of long chains of amino acids. These amino acids are linked together by peptide bonds, forming polypeptides that fold into specific three-dimensional shapes to perform various functions in the body, such as enzymes, hormones, and structural components.
Complex carbohydrates, nucleic acids, and lipids are different types of macromolecules. Complex carbohydrates are made up of sugar molecules (monosaccharides) linked together, nucleic acids like DNA and RNA are made of nucleotide units, and lipids consist of fatty acids and glycerol. Thus, only proteins are formed from amino acids.