答案1
\documentclass{book}
\usepackage{tikz-cd}
\begin{document}
\begin{tikzcd}
\bullet\ar[r]\ar[d]\ar[rd]\ar[loop, <->, in=170,out=100,looseness=5]&[10pt] \bullet\ar[d]\ar[loop, <->, in=10,out=80,looseness=5] \\
\bullet\ar[r]\ar[loop, <->, in=190,out=-100,looseness=5]& \bullet\ar[loop, <->, in=-80,out=-10,looseness=5]
\end{tikzcd}
\end{document}