$1$ $\,.\,\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,H\,\,\,\,\,\,\,\,\,\,\,\,\,$
$2$ $\,.\,\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,C{H_3}\,\,\,\,\,\,\,\,\,$
$3$ $\,.\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,C{H_2}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \,\, - \,\,H\,\,\,\,\,\,$
$4$ $\,.\,\,C{H_3}\, - \,\,\mathop C\limits_{\mathop {||}\limits_O } \, - \,\,C{H_2}\, - \,\mathop C\limits_{\mathop {||}\limits_O } \, - \,\,C{H_3}$
$I$ || $II$ || $III$