b
\((b)\) Amino acids which combine into peptide chains to form the building blocks  of a rest array of proteins are all \(L-\) stereoisomers (left handed) 
Glycine                                \(NH_2 - CH_2 - COOH\)

\(L\)-Amino acid                   \(\begin{matrix}
   N{{H}_{2}}-CH-COOH  \\
   |\,\,\,\,\,\,\,\,\,\,  \\
   R\,\,\,\,\,\,\,\,\,\,  \\
\end{matrix}\)