我正在参加考试，我想使用 Courier 字体，但生成的文档没有 Courier。有人能帮我生成我需要的文档吗？
\tracinggroups=1
\documentclass[12pt,addpoints,answers]{exam}
\usepackage{m-ch-en}
\usepackage{chemfig}
\usepackage{courier}
\usepackage{here}
\begin{document}
\begin{questions}
\question Eyepiece graticules and stage micrometers are used to measure cells.\\
Which is the correct reason why an eyepiece graticule is calibrated?
\begin{choices}
\choice An eyepiece graticule can be used to make measurements.
\choice An eyepiece graticule is magnified by the objective lens.
\choice An eyepiece graticule magnifies the specimen.
\choice An eyepiece graticule makes comparisons.
\end{choices}
\question When mucus is secreted from a goblet cell in the trachea, these events take place.
\begin{enumerate}
\item addition of carbohydrate to protein
\item fusion of the vesicle with the plasma membrane
\item secretion of a glycoprotein
\item separation of a vesicle from the Golgi apparatus
What is the sequence in which these events take place?
\end{enumerate}
What is the sequence in which these events take place?
\begin{choices}
\choice $1 \rightarrow 4 \rightarrow 2 \rightarrow 3$
\choice $1 \rightarrow 4 \rightarrow 3 \rightarrow 2$
\choice $4 \rightarrow 1 \rightarrow 2 \rightarrow 3$
\choice $4 \rightarrow 1 \rightarrow 3 \rightarrow 2$
\end{choices}
\question What is a function of the smooth endoplasmic reticulum?\\
\begin{oneparchoices}
\choice antibody synthesis
\choice enzyme synthesis
\choice protein synthesis
\choice steroid synthesis
\end{oneparchoices}
\question Which of the following can decrease the fluidity of the cell surface membrane?
\begin{itemize}
\item double bonds between carbon atoms in the fatty acid chains
\item cholesterol
\item fatty acids having longer chains
\end{itemize}
\begin{choices}
\choice 1, 2 and 3
\choice 1 and 2 only
\choice 2 and 3 only
\choice 3 only
\end{choices}
\end{questions}
\end{document}