Keeping a diagram + question on the same page/column with the exam class

Question

I use the exam class to write multiple choice questions, and I frequently use tikz to make a diagram that precedes a question. How can I make sure that each diagram+question doesn't break across a column or page break?

Wrapping the tikzpicture and question in a minipage works for the 2nd question onward, but not for the very first question after \begin{questions}. Is there a way I can do something similar for the first question?

This works:

\documentclass[twocolumn]{exam}
\usepackage{tikz}

\begin{document}
\twocolumn

\begin{questions}

  \question What's the length of the line above?
  \begin{choices}
  \choice 1
  \choice 8
  \end{choices}

  \begin{minipage}{\linewidth}
  \begin{tikzpicture}
  \draw (0,0) -- (2,0);
  \end{tikzpicture}

  \question What's the length of the line above?
  \begin{choices}
  \choice 2
  \choice 1
  \end{choices}
  \end{minipage}

\end{questions}

\end{document}

But this doesn't compile (presumably since \begin{questions} expects \question right away):

\documentclass[twocolumn]{exam}
\usepackage{tikz}

\begin{document}
\twocolumn

\begin{questions}

  \begin{minipage}{\linewidth}
  \begin{tikzpicture}
  \draw (0,0) -- (2,0);
  \end{tikzpicture}

  \question What's the length of the line above?
  \begin{choices}
  \choice 2
  \choice 1
  \end{choices}
  \end{minipage}      

  \question What's the length of the line above?
  \begin{choices}
  \choice 1
  \choice 8
  \end{choices}

\end{questions}

\end{document}

Answer 1

Welcome to TeX.SE! I am not sure I understand the purpose of the minipage here. Regardless of whether or not you want to use it, here is a simple cheat that allows you to add a picture above a question. It adds an item, but does not print the number and makes sure the counter does not get increased.

\documentclass[twocolumn]{exam}
\usepackage{tikz}
\newenvironment{pictureabovequestion}{\color{white}  \item\color{black}}{\addtocounter{question}{-1}}
\begin{document}
\twocolumn

\begin{questions}

\begin{pictureabovequestion}
  \begin{tikzpicture}
  \draw (0,0) -- (2,0);
  \end{tikzpicture}
\end{pictureabovequestion}    
  \question What's the length of the line above?
  \begin{choices}
  \choice 1
  \choice 8
  \end{choices}


\begin{pictureabovequestion}
  \begin{tikzpicture}
  \draw[blue] (0,0) -- (1,0);
  \end{tikzpicture}
\end{pictureabovequestion}    
  \question What's the length of the line above?
  \begin{choices}
  \choice 2
  \choice 1
  \end{choices}

\end{questions}

\end{document}