多列分页符问题

Question

我有以下内容，并且在 之前出现分页符multicols。我尝试过\vfill\break之前\break和之后multicols。我也尝试过multicols*。

需要\vfill在图表前添加...

Graph the function
\[
f(x)=x^{3}.
\]
\begin{multicols}{2}
\begin{enumerate}
\item \begin{tikzpicture}
    \begin{axis}[
        scale=0.75,
        axis x line=center,
        axis y line=center,
        xtick={-5,-4,...,5},
        ytick={-5,-4,...,5},
        xlabel={$x$},
        ylabel={$y$},
        xlabel style={below right},
        ylabel style={above left},
        xmin=-5.5,
        xmax=5.5,
        ymin=-5.5,
        ymax=5.5] 
    \addplot [mark=none,domain=-4:4] {x^2}; 
    \end{axis}
\end{tikzpicture}
\item \begin{tikzpicture}
    \begin{axis}[
        scale=0.75,
        axis x line=center,
        axis y line=center,
        xtick={-5,-4,...,5},
        ytick={-5,-4,...,5},
        xlabel={$x$},
        ylabel={$y$},
        xlabel style={below right},
        ylabel style={above left},
        xmin=-5.5,
        xmax=5.5,
        ymin=-5.5,
        ymax=5.5] 
    \addplot [mark=none,domain=-4:4] {x^3}; 
    \end{axis}
\end{tikzpicture}
\item \begin{tikzpicture}
    \begin{axis}[
        scale=0.75,
        axis x line=center,
        axis y line=center,
        xtick={-5,-4,...,5},
        ytick={-5,-4,...,5},
        xlabel={$x$},
        ylabel={$y$},
        xlabel style={below right},
        ylabel style={above left},
        xmin=-5.5,
        xmax=5.5,
        ymin=-5.5,
        ymax=5.5] 
    \addplot [mark=none,domain=-4:4] {-x^2}; 
    \end{axis}
\end{tikzpicture}
\item \begin{tikzpicture}
    \begin{axis}[
        scale=0.75,
        axis x line=center,
        axis y line=center,
        xtick={-5,-4,...,5},
        ytick={-5,-4,...,5},
        xlabel={$x$},
        ylabel={$y$},
        xlabel style={below right},
        ylabel style={above left},
        xmin=-5.5,
        xmax=5.5,
        ymin=-5.5,
        ymax=5.5] 
    \addplot [mark=none,domain=-4:4] {-x^3}; 
    \end{axis}
\end{tikzpicture}
\end{enumerate}
\end{multicols}\hfill\rule{0.2\columnwidth}{1pt}