Explanation:
(d) In proteins amide group is present
\({( - NH - \mathop C\limits_{\mathop |\limits_R } H - \underbrace {\mathop C\limits_{\mathop {||}\limits_O } - NH - \mathop C\limits_{\mathop |\limits_R } H}_{\,\,\,{\text{Amino or}}\,\,\,{\text{peptide bond}}} - \mathop C\limits_{\mathop {||}\limits_O } - )_n}\)