Let $G= (V,E)$ be a simple, undirected graph. A set $C\subseteq V$ is said to be an edge cover if for all $e\in E$ we have $e\cap C \neq \emptyset$.
It is most satisfying to find an edge cover $C$ such that every edge is covered exactly once (that is, $|C\cap e| = 1$ for all $e\in E$) -- but unfortunately this is only possible if $G$ does not contain odd circles (i.e. $\chi(G) \leq 2$).
However: given any graph $G$, is it always possible to find an edge cover $C\subseteq V(G)$ such that the number of edges $e\in E$ with $e\subseteq C$ is at most the number of odd circles in $G$?