\item \self Tick all properties that apply to a reduced and ordered binary decision diagram.
\begin{itemize}
  \item[$\square$] A reduced and ordered BDD is a canonical representation of the formula it represents, for any fixed variable order.
  \item[$\square$] Since it is reduced, the number of nodes in the reduced and ordered BDD does not exceed $2n^2$, where $n$ is the number of variables.
  \item[$\square$] The graph of an BDD may contain cycles.
  \item[$\square$] A BDD represents a propositional formula as directed acyclic graph (DAG).
  \item[$\square$] Every node with two non-complemented outgoing edges has two distinct child nodes.
  \item[$\square$] No two nodes in an reduced and ordered BDD represent the same cofactor.
\end{itemize}