\documentclass[12pt]{standalone}

\usepackage{tikz}
\usepackage{ctex}

\begin{document}
\begin{tikzpicture}[x=2cm,y=2cm]

\begin{scope}[every node/.style={circle,draw,minimum size=10mm}]
    \node (u) at (0.5,0) {$u$};
    \node (v) at (2,0) {$v$};
    \node (i1) at (0,1) {$i$};
    \node (i2) at (2.5,2) {$i$};
\end{scope}

\draw (u) -- node[circle,fill] {} node[below=6pt] {$c$} (v);
\draw (i1) -- (u);
\draw (i2) -- (v);

\end{tikzpicture}
\end{document}
