在考试类中使用 \printanswers 命令时，带有图形选项的多项选择题会出现错误

Question

这个问题已从这个问题有附加功能。但是，当我使用\printanswers命令时，代码给出了以下错误：

! Extra }, or forgotten \endgroup.
\endmulticols ->\par \if@boxedmulticols \egroup 
                                                \balance@columns \return@non...
l.24             \end{multicols}

? 

我的 MWE 代码根据以下建议进行了修改贡萨洛·梅迪纳与之一起使用时\noprintanswers如下所示：

\documentclass{exam}
\usepackage{multicol}
\usepackage{graphicx}
\usepackage{adjustbox}
%\printanswers
\noprintanswers
\begin{document}
\begin{questions}
    \question 
    \begin{minipage}[t]{0.65\linewidth}
    Consider the network graph shown in the figure, which of the following is NOT a \textit{tree} of this graph?
            \begin{choices}
        \begin{multicols}{2}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-a}}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-b}}
        \end{multicols}\par
        \begin{multicols}{2}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-c}}
                \CorrectChoice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-a}}
        \end{multicols}
            \end{choices}
\end{minipage}\hfill%
    \begin{adjustbox}{minipage={0.30\linewidth},valign=t}
    \includegraphics[width=\linewidth]{example-image-a} 
\end{adjustbox}
\end{questions}
\end{document}

当\printanswers使用命令时，它应该给出如下输出，突出显示partlabel与以下内容相对应的内容\CorrectChoice：

\printanswer有任何建议可以解决在给定代码中使用命令时出现的错误！

Answer 1

更新在这个解决方案中，我们定义了multichoices像多列一样工作的新环境，默认情况下它有两列，但如果需要可以设置更多列。

\makeatletter
\newenvironment{multichoices}[1][2]{%
\begin{multicols}{#1}}{%
\if@correctchoice \endgroup \fi
\end{multicols}}
\makeatother

平均能量损失

\documentclass{exam}
\usepackage{multicol}
\usepackage{graphicx}
\usepackage{adjustbox}
\printanswers
%\noprintanswers

\makeatletter
\newenvironment{multichoices}[1][2]{%
\begin{multicols}{#1}}{%
\if@correctchoice \endgroup \fi
\end{multicols}}
\makeatother

\begin{document}
\begin{questions}
    \question 
    \begin{minipage}[t]{0.65\linewidth}
    Consider the network graph shown in the figure, which of the following is NOT a \textit{tree} of this graph?
            \begin{choices}
        \begin{multichoices}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-a}}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-b}}
        \end{multichoices}\par
        \begin{multichoices}
                \CorrectChoice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-a}}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-c}}
        \end{multichoices}
            \end{choices}
\end{minipage}\hfill%
    \begin{adjustbox}{minipage={0.30\linewidth},valign=t}
    \includegraphics[width=\linewidth]{example-image-a} 
\end{adjustbox}


    \question 
    \begin{minipage}[t]{0.65\linewidth}
    Consider the network graph shown in the figure, which of the following is NOT a \textit{tree} of this graph?
            \begin{choices}
        \begin{multichoices}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-a}}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-b}}
        \end{multichoices}\par
        \begin{multichoices}
                \choice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-c}}
                \CorrectChoice
                    \adjustbox{valign=t}{\includegraphics[scale=0.2]{example-image-a}}
        \end{multichoices}
            \end{choices}
\end{minipage}\hfill%
    \begin{adjustbox}{minipage={0.30\linewidth},valign=t}
    \includegraphics[width=\linewidth]{example-image-a} 
\end{adjustbox}

    \question 
    \begin{minipage}[t]{0.65\linewidth}
    Consider the network graph shown in the figure, which of the following is NOT a \textit{tree} of this graph?
            \begin{choices}
        \begin{multichoices}
                \choice
                       bla bla
                \choice
                       bla bla
        \end{multichoices}\par
        \begin{multichoices}
                \choice
                       bla bla
                \CorrectChoice
                    bla bla
        \end{multichoices}
            \end{choices}
\end{minipage}\hfill%
    \begin{adjustbox}{minipage={0.30\linewidth},valign=t}
    \includegraphics[width=\linewidth]{example-image-a} 
\end{adjustbox}


    \question 
    \begin{minipage}[t]{0.65\linewidth}
    Consider the network graph shown in the figure, which of the following is NOT a \textit{tree} of this graph?
            \begin{choices}
        \begin{multichoices}
                \choice
                       bla bla
                \choice
                       bla bla
        \end{multichoices}\par
        \begin{multichoices}
                \CorrectChoice
                       bla bla
                \choice
                    bla bla
        \end{multichoices}
            \end{choices}
\end{minipage}\hfill%
    \begin{adjustbox}{minipage={0.30\linewidth},valign=t}
    \includegraphics[width=\linewidth]{example-image-a} 
\end{adjustbox}

\end{questions}
\end{document}