\newcounter{choix}
\newenvironment{reponses}{
  \setcounter{choix}{0}%
  \begin{list}{}{
  \setlength{\labelwidth}{1cm}%
  \setlength{\labelsep}{5mm}%
  \setlength{\itemindent}{0cm}%
  \setlength{\itemsep}{5pt}%
  \@beginparpenalty=100000%
  \@itempenalty=100000}%
  }{\end{list}}


\newcommand{\choix}[2][]{
  \stepcounter{choix}%
  \ifthenelse{\boolean{tb@mode@correction}}{%
    \def\qcm@tempa{#1}%
    \ifx\qcm@tempa\@empty%
      \item[\hfill(\alph{choix})\hfill] #2%
    \else
      \vspace{-\fboxsep}\item[\hfill\fbox{(\alph{choix})}\hfill] #2\vspace{-\fboxsep}%
    \fi
  }{
    \item[\hfill(\alph{choix})\hfill] #2%
  }
}

\newcommand{\justif}[1]{
  \ifthenelse{\boolean{tb@mode@correction}}{%
    {\color{red}#1}
  }{}
}
