I was wondering whether [Martin Sleziak's][1] excellent answer to [this question][2] could be generalized: Suppose that $S$ is an infinite set, and let ${\cal L}$ be a collection of subsets of $S$ such that for all $L_1\neq L_2\in {\cal L}$ the intersection $L_1\cap L_2$ contains at most one element. Is there $M\subseteq S$ such that 1. $M$ intersects all the elements of ${\cal L}$, but 2. for all $m\in M$, the set $M\setminus\{m\}$ no longer intersects all the elements of $\cal L$ ? [1]: https://mathoverflow.net/users/8250/martin-sleziak [2]: https://mathoverflow.net/questions/278143/meeting-a-set-of-lines-in-mathbbrn