[Tex/LaTex] Subcolumns with multicol and the exam class

exammulticolspacing

I'm using the multicol package with the exam class to create 2 sub-columns within a multicols environment for checkbox answers when the answers are short and one word. There is a significant amount of whitespace between answers in the sub-columns, however, and \setlength\columnsep{Xpt} doesn't seem to bring them closer together.

In the example below, the space between the two columns in the second question needs to be compacted: 

\documentclass[10pt]{exam}
\usepackage{multicol}
\setlength\columnsep{40pt}
\begin{document}
\begin{multicols}{2}[\section{My Form}]
\begin{questions}
\question Is this a question\hfill
\mbox{
    \begin{oneparcheckboxes}
        \choice Yes
        \choice No
    \end{oneparcheckboxes}
}
\question These columns are too far apart
\begin{multicols}{2}
    \begin{checkboxes}
        \choice Apple
        \choice Banana
        \choice Cucumber
        \choice Eggplant
        \choice Fruit
        \choice Grapes
    \end{checkboxes}
\end{multicols}
\question Comments:\ \hrulefill
\end{questions}
\end{multicols}
\end{document}

Best Answer

But changing columnsep reduces the spacing (perhaps I am misunderstanding the problem?):

\documentclass[10pt]{exam}
\usepackage{multicol}
\setlength\columnsep{40pt}
\begin{document}

\begin{multicols}{2}[\section{My Form}]

\begin{questions}
\question Is this a question\hfill
\mbox{
    \begin{oneparcheckboxes}
        \choice Yes
        \choice No
    \end{oneparcheckboxes}
}
\question These columns are closer now
\setlength\columnsep{-1cm}
\begin{multicols}{2}
    \begin{checkboxes}
        \choice Apple
        \choice Banana
        \choice Cucumber
        \choice Eggplant
        \choice Fruit
        \choice Grapes
    \end{checkboxes}
\end{multicols}
\question Comments:\ \hrulefill
\end{questions}
\end{multicols}
\end{document}

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