20 different link together to form chains. a protein is composed of one or more of these chains which are twisted and folded into a particular shape.

Amino acids; peptide

Explanation:

20 different AMINO ACIDS link together to form chains. A protein is composed of one or more of these PEPTIDE chains which are twisted and folded into a particular shape.

There exists 20 amino acids capable of forming protein in the Human body. At least two amino acids are joined together by a peptide bond to form polypeptide chains that are then held together by hydrogen bonds in twisted alpha helical structures to form proteins.

Amino acid, polypeptide/polynucleotide chains

Explanation: Amino acids are usually the building blocks of protein hence,every protein is made up of one or more amino acids.

A protein consist of one or more polypeptide chain that is folded into a helix shape. This shape is to prevent the easy degradation of the components that makes up the polypeptide because it is water loving and can easy degrade.

the correct option is option d