Nylon 2-nylon 6 is built from glycine ($\mathrm{H}{}_2\mathrm{N}-\mathrm{CH}{}_2-\mathrm{COOH}$) and 6-aminohexanoic acid ($\mathrm{H}{}_2\mathrm{N}-(\mathrm{CH}{}_2){}_5-\mathrm{COOH}$) joined alternately by amide bonds. Taking C = 12, H = 1, N = 14, O = 16, the molar mass of the repeat unit containing one residue of each acid, in $\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$, is

1. A$206$
2. B$188$
3. C$113$
4. D$170$