$1.\,\,\,\begin{array}{*{20}{c}}
{C{H_3} - C - {O^ - }} \\
{\,\,\,||} \\
{\,\,\,O}
\end{array}$ $2.\,\,CH_3O^-$ $3.\,\,CN^-$
$(I)$ $CH_2 = CH - C \equiv CH$
$(II)$ $CH \equiv C - C\equiv CH$
$(III)$ $CH_3 - CH = CH_2$
$(IV) $ $CH_2 = CH - C = CH_2$