Identify the incorrect statement from the following

• A

  In $\mathrm{\alpha }-$helical structure, the $-\mathrm{NH}-$ group of one amino acid residue is hydrogen bonded to $-\mathrm{CO}-$ of the other amino acid residue of adjacent turn of the same polypeptide chain

• B

  In $\mathrm{\beta }-$pleated structure, all peptide chains are streched out to nearly maximum extension

• C

  In $\mathrm{\beta }-$pleated structure, peptide chains are laid side by side and held together by inter molecular hydrogen bonding

• D

  In $\mathrm{\alpha }-$helical structure, polypeptide chain forms all possible hydrogen bonds by twisting into a left handed screw(helix)