前言

在 $\LaTeX$ 中排版选择题的选项可能的方法有：

表格
tasks 宏包
bhcexam 文档类

之前排选项的时候都是用不同的表格去排的，需要人工判断用哪个命令，非常繁琐，所以弄一个自动判断用哪个命令的代码就很有必要了。

正文

我参考 bhcexam 文档类后，写出了自己的一套排版选项的代码。

% \usepackage{calc,ifthen}

\newlength{\choicelengtha}
\newlength{\choicelengthb}
\newlength{\choicelengthc}
\newlength{\choicelengthd}
\newlength{\maxlength}

\makeatletter
\newcommand{\fourch}[4]{
  \par
  \settowidth{\choicelengtha}{A．#1}
  \settowidth{\choicelengthb}{B．#2}
  \settowidth{\choicelengthc}{C．#3}
  \settowidth{\choicelengthd}{D．#4}
  \ifthenelse{\lengthtest{\choicelengtha>\choicelengthb}}{\setlength{\maxlength}{\choicelengtha}}{\setlength{\maxlength}{\choicelengthb}}
  \ifthenelse{\lengthtest{\choicelengthc>\maxlength}}{\setlength{\maxlength}{\choicelengthc}}{}
  \ifthenelse{\lengthtest{\choicelengthd>\maxlength}}{\setlength{\maxlength}{\choicelengthd}}{}
  \ifthenelse{\lengthtest{\maxlength>0.8\linewidth}}
  {%
    \noindent%
    \begin{tabular}{@{}p{\linewidth}@{}}
      \setlength\tabcolsep{0pt}
      \@hangfrom{\textsf A．}#1 \\
      \@hangfrom{\textsf B．}#2 \\
      \@hangfrom{\textsf C．}#3 \\
      \@hangfrom{\textsf D．}#4 \\
    \end{tabular}
  }%
  {%
    \ifthenelse{\lengthtest{\maxlength>0.22\linewidth}}
    {%
      \noindent%
      \begin{tabular}{@{}p{0.48\linewidth}@{\hspace*{0.04\linewidth}}p{0.48\linewidth}@{}}
        \setlength\tabcolsep{0pt}
        \@hangfrom{\textsf A．}#1 & \@hangfrom{\textsf B．}#2 \\
        \@hangfrom{\textsf C．}#3 & \@hangfrom{\textsf D．}#4 \\
      \end{tabular}
    }%
    {%
      \noindent%
      \begin{tabular}{@{}*{3}{p{0.22\linewidth}@{\hspace*{0.04\linewidth}}}p{0.22\linewidth}@{}}
        \setlength\tabcolsep{0pt}
        \@hangfrom{\textsf A．}#1  & \@hangfrom{\textsf B．}#2 & \@hangfrom{\textsf C．}#3 & \@hangfrom{\textsf D．}#4 \\
      \end{tabular}
    }%
  }%
  \unskip \unskip 
}
\makeatother

分析

逐条去解释命令的作用

新增长度变量，为后面长度比较做铺垫

\newlength{\choicelengtha}
\newlength{\choicelengthb}
\newlength{\choicelengthc}
\newlength{\choicelengthd}
\newlength{\maxlength}

在 \makeatletter 和 \makeatother 中将 @ 作为一个字母看待
\makeatletter
...
\makeatother

读取 A、B、C、D 及其选项的总长度

\settowidth{\choicelengtha}{A．#1}
\settowidth{\choicelengthb}{B．#2}
\settowidth{\choicelengthc}{C．#3}
\settowidth{\choicelengthd}{D．#4}

作判断，谁长取谁为最大值

\ifthenelse{\lengthtest{\choicelengtha>\choicelengthb}}{\setlength{\maxlength}{\choicelengtha}}{\setlength{\maxlength}{\choicelengthb}}
\ifthenelse{\lengthtest{\choicelengthc>\maxlength}}{\setlength{\maxlength}{\choicelengthc}}{}
\ifthenelse{\lengthtest{\choicelengthd>\maxlength}}{\setlength{\maxlength}{\choicelengthd}}{}

如果最大值的长度大于 0.8\linewidth 就执行后面括号里的命令
\ifthenelse{\lengthtest{\maxlength>0.8\linewidth}}{...}

每个选项单独排一行

\noindent%
\begin{tabular}{@{}p{\linewidth}@{}}
  \setlength\tabcolsep{0pt}
  \@hangfrom{\textsf A．}#1 \\
  \@hangfrom{\textsf B．}#2 \\
  \@hangfrom{\textsf C．}#3 \\
  \@hangfrom{\textsf D．}#4 \\
\end{tabular}

tabular 环境的表格项前后的间距为 0pt

\setlength\tabcolsep{0pt}
取消前后多余的间距

@{}p{\linewidth}@{}
产生悬挂缩进的效果

\@hangfrom

完整的例子

\documentclass{ctexart}
\usepackage{calc,ifthen}

\newlength{\choicelengtha}
\newlength{\choicelengthb}
\newlength{\choicelengthc}
\newlength{\choicelengthd}
\newlength{\choicelengthe}
\newlength{\maxlength}

\makeatletter
\newcommand{\fourch}[4]{
  \par
  \settowidth{\choicelengtha}{A．#1}
  \settowidth{\choicelengthb}{B．#2}
  \settowidth{\choicelengthc}{C．#3}
  \settowidth{\choicelengthd}{D．#4}
  \ifthenelse{\lengthtest{\choicelengtha>\choicelengthb}}{\setlength{\maxlength}{\choicelengtha}}{\setlength{\maxlength}{\choicelengthb}}
  \ifthenelse{\lengthtest{\choicelengthc>\maxlength}}{\setlength{\maxlength}{\choicelengthc}}{}
  \ifthenelse{\lengthtest{\choicelengthd>\maxlength}}{\setlength{\maxlength}{\choicelengthd}}{}
  \ifthenelse{\lengthtest{\maxlength>0.8\linewidth}}
  {%
    \noindent%
    \begin{tabular}{@{}p{\linewidth}@{}}
      \setlength\tabcolsep{0pt}
      \@hangfrom{\textsf A．}#1 \\
      \@hangfrom{\textsf B．}#2 \\
      \@hangfrom{\textsf C．}#3 \\
      \@hangfrom{\textsf D．}#4 \\
    \end{tabular}
  }%
  {%
    \ifthenelse{\lengthtest{\maxlength>0.22\linewidth}}
    {%
      \noindent%
      \begin{tabular}{@{}p{0.48\linewidth}@{\hspace*{0.04\linewidth}}p{0.48\linewidth}@{}}
        \setlength\tabcolsep{0pt}
        \@hangfrom{\textsf A．}#1 & \@hangfrom{\textsf B．}#2 \\
        \@hangfrom{\textsf C．}#3 & \@hangfrom{\textsf D．}#4 \\
      \end{tabular}
    }%
    {%
      \noindent%
      \begin{tabular}{@{}*{3}{p{0.22\linewidth}@{\hspace*{0.04\linewidth}}}p{0.22\linewidth}@{}}
        \setlength\tabcolsep{0pt}
        \@hangfrom{\textsf A．}#1  & \@hangfrom{\textsf B．}#2 & \@hangfrom{\textsf C．}#3 & \@hangfrom{\textsf D．}#4 \\
      \end{tabular}
    }%
  }%
  \unskip\unskip
}
\makeatother

\begin{document}
\fourch{劳仑衣普桑，认至将指点效则机，最你更枝。想极整月正进好志次回总般，段然取向使张规军证回，世市总李率英茄持伴。用阶千样响领交出，器程办管据家元写，名其直金团。}{test}{test}{test}

\fourch{劳仑衣普桑，认至将指点效则机，最你效则机，最你指点}{test}{test}{test}

\fourch{劳仑衣普桑，认至将指点效则机，最你效则机，最你指}{test}{test}{test}

\fourch{劳仑衣普桑}{test}{test}{test}
\end{document}

效果图：