Let ${ \rm Z}(G)$ and ${ \rm gp}(G)$ be the zero forcing number and the general position number of a graph $G$, respectively. Known results imply that ${ \rm gp}(T)\ge { \rm Z}(T) + 1$ holds for every nontrivial tree $T$. It is proved that the result extends to block graphs. For connected, unicyclic graphs $G$ it is proved that ${ \rm gp}(G) \ge { \rm Z}(G)$. The result extends neither to bicyclic graphs nor to quasi-trees. Nevertheless, a large class of quasi-trees is found for which ${ \rm gp}(G) \ge { \rm Z}(G)$ holds.
Categories: math.CO