\begin{tikzpicture}%[scale=1,transform shape]

  \begin{class}[text width=2cm]{C}{-1,0}
    \attribute{attrC : C}
  \end{class}
 
  \begin{class}[text width=2cm]{DAB}{2,0}
    \attribute{attrD : C}
    \attribute{attrB1 : C}
    \attribute{attrB2 : C}
  \end{class}

\end{tikzpicture}