Solution
= Solution
{c}
The <closure> $\overline A$ is the intersection of all closed subsets of $X$ containing $A$. It is the smallest such closed subset. Equivalently, $x\in\overline A$ exactly when every <open neighborhood> of $x$ meets $A$.
= Solution
{c}
The <closure> $\overline A$ is the intersection of all closed subsets of $X$ containing $A$. It is the smallest such closed subset. Equivalently, $x\in\overline A$ exactly when every <open neighborhood> of $x$ meets $A$.