答案1
您可以执行以下操作:
\documentclass{book}
\usepackage{graphicx,subcaption}
\begin{document}
\begin{figure}
\begin{subfigure}[b]{.3\textwidth}
\centering\includegraphics[width=\textwidth]{example-image}
\caption{A subfigure}\label{fig:1a}
\end{subfigure}\hfill
\begin{subfigure}[b]{.3\textwidth}
\centering\includegraphics[width=\textwidth]{example-image}
\caption{Another subfigure}\label{fig:1b}
\end{subfigure}\hfill
\begin{subfigure}[b]{.3\textwidth}
\centering\includegraphics[width=\textwidth]{example-image}
\caption{Another subfigure}\label{fig:1c}
\end{subfigure}\hfill
\begin{subfigure}[b]{.3\textwidth}
\centering\includegraphics[width=\textwidth]{example-image}
\caption{Another subfigure}\label{fig:1d}
\end{subfigure}\hfill
\begin{subfigure}[b]{.3\textwidth}
\centering\includegraphics[width=\textwidth]{example-image}
\caption{Another subfigure}\label{fig:1e}
\end{subfigure}\hfill
\begin{subfigure}[b]{.3\textwidth}
\centering\includegraphics[width=\textwidth]{example-image}
\caption{Another subfigure}\label{fig:1f}
\end{subfigure}
\caption{A figure}\label{fig:1}
\end{figure}
\end{document}