Amino acids can be classified as $\alpha$,$\beta$,$\gamma$,$\delta$ and so on,depending upon the relative positions of the amino group with respect to the carboxyl group. Which type of amino acids form polypeptide chains in proteins?

(A) Only $\alpha$-amino acids are the building blocks of proteins. In these,the amino group $(-NH_2)$ is attached to the $\alpha$-carbon atom,which is the carbon atom adjacent to the carboxylic acid group $(-COOH)$. These $\alpha$-amino acids undergo polymerization through peptide bond formation to create polypeptide chains in proteins.