El entorno de piezas en la clase de examen no se muestra correctamente

Question

En el NQMWE (ejemplo de trabajo no del todo mínimo) a continuación, una pregunta tiene dos parts:

\documentclass[addpoints]{exam}

\pointsinrightmargin

\begin{document}

\header{English 245}{Quiz on \emph{Childhood's End}, pp. 1--23}{2019/02/26}

\vspace{2mm}

\noindent Name: \makebox[0.5\textwidth]{\dotfill}

\vspace{5mm}

\noindent Score: \makebox[1in]{\dotfill} of a possible \numpoints ~points

\begin{questions}
\question The Overlords make two demonstrations of their powers. What are they?
    \begin{parts}
        \part [1]
            \begin{solution}[1in]
            They destroy an incoming missile
            \end{solution}
        \part [1]
            \begin{solution}[1in]
            They block out the sun over Cape Town.
            \end{solution}
    \end{parts}

\question [1] The Overlords communicate through which medium?
\begin{choices}
\choice Written messages
\correctchoice Speech
\choice Video
\choice Musical tones
\end{choices}
\question [1] The Overlords' human liaison works for which organization?
\begin{choices}
\correctchoice The United Nations
\choice The World Health Organization
\choice The US government
\choice The Soviet government
\end{choices}
\question [1] The human opposition to the Overlords focuses on which of the following?
\begin{choices}
\choice \label{choice:cruelty} The cruelty of their rule
\choice \label{choice:concealment}The fact that they choose not to reveal themselves to their subjects
\choice \label{choice:sovereignty}The loss of human sovereignty
\correctchoice \ref{choice:concealment} and ~\ref{choice:sovereignty}, but not ~\ref{choice:cruelty}
\choice \ref{choice:cruelty} and ~\ref{choice:sovereignty}, but not ~\ref{choice:concealment}
\end{choices}
\end{questions}
\end{document}

Cuando lo compilo, la partsprimera pregunta no aparece, pero todo lo demás funciona correctamente (ver imagen a continuación). (Es por eso que incluí el archivo completo: todas las opciones, etiquetas, etc. funcionan bien, excepto en el partsentorno).

¿Qué pasa aquí?

Answer 1

No proporcionó texto adicional para \parts [1]imprimir, por lo que las etiquetas de las piezas no se imprimen. Puede agregar mensajes de texto para cada pieza (por ejemplo, "Demostración 1") o puede crear una línea de espesor cero para que funcione como mensaje de texto para mostrar solo la etiqueta de la pieza. Agregué un ejemplo de cada uno a su código.

\documentclass[addpoints]{exam}

\pointsinrightmargin

\begin{document}

\header{English 245}{Quiz on \emph{Childhood's End}, pp. 1--23}{2019/02/26}

\vspace{2mm}

\noindent Name: \makebox[0.5\textwidth]{\dotfill}

\vspace{5mm}

\noindent Score: \makebox[1in]{\dotfill} of a possible \numpoints ~points

\begin{questions}
\question The Overlords make two demonstrations of their powers. What are they?
    \begin{parts}
        \part [1] Demonstration 1: % Use a text prompt
            \begin{solution}[1in]
            They destroy an incoming missile
            \end{solution}
        \part [1] \rule{1em}{0pt}  % Use an 0 thickness line
            \begin{solution}[1in]
            They block out the sun over Cape Town.
            \end{solution}
    \end{parts}

\question [1] The Overlords communicate through which medium?
\begin{choices}
\choice Written messages
\correctchoice Speech
\choice Video
\choice Musical tones
\end{choices}
\question [1] The Overlords' human liaison works for which organization?
\begin{choices}
\correctchoice The United Nations
\choice The World Health Organization
\choice The US government
\choice The Soviet government
\end{choices}
\question [1] The human opposition to the Overlords focuses on which of the following?
\begin{choices}
\choice \label{choice:cruelty} The cruelty of their rule
\choice \label{choice:concealment}The fact that they choose not to reveal themselves to their subjects
\choice \label{choice:sovereignty}The loss of human sovereignty
\correctchoice \ref{choice:concealment} and ~\ref{choice:sovereignty}, but not ~\ref{choice:cruelty}
\choice \ref{choice:cruelty} and ~\ref{choice:sovereignty}, but not ~\ref{choice:concealment}
\end{choices}
\end{questions}
\end{document}

Answer 2

El problema es el solutionentorno dentro de \parts:

\begin{document}

\header{English 245}{Quiz on \emph{Childhood's End}, pp. 1--23}{2019/02/26}

\vspace{2mm}

\noindent Name: \makebox[0.5\textwidth]{\dotfill}

\vspace{5mm}

\noindent Score: \makebox[1in]{\dotfill} of a possible \numpoints ~points

\begin{questions}
\question The Overlords make two demonstrations of their powers. What are they?
    \begin{parts}
        \part [1]
            %\begin{solution}[1in]
            They destroy an incoming missile
            %\end{solution}
        \part [1]
            %\begin{solution}[1in]
            They block out the sun over Cape Town.
            %\end{solution}
    \end{parts}

\question [1] The Overlords communicate through which medium?
\begin{choices}
\choice Written messages
\correctchoice Speech
\choice Video
\choice Musical tones
\end{choices}
\question [1] The Overlords' human liaison works for which organization?
\begin{choices}
\correctchoice The United Nations
\choice The World Health Organization
\choice The US government
\choice The Soviet government
\end{choices}
\question [1] The human opposition to the Overlords focuses on which of the following?
\begin{choices}
\choice \label{choice:cruelty} The cruelty of their rule
\choice \label{choice:concealment}The fact that they choose not to reveal themselves to their subjects
\choice \label{choice:sovereignty}The loss of human sovereignty
\correctchoice \ref{choice:concealment} and ~\ref{choice:sovereignty}, but not ~\ref{choice:cruelty}
\choice \ref{choice:cruelty} and ~\ref{choice:sovereignty}, but not ~\ref{choice:concealment}
\end{choices}
\end{questions}
\end{document}