---

Solution

Statement I says:

Grandparent is a parent of one's parent.

This is correct.

For example, if $g$ is parent of $p$ and $p$ is parent of $c$, then $g$ is grandparent of $c$.

Now check Statement II:

$\forall g,c\ grandparent(g,c)\Leftrightarrow \exists p\ parent(g,p)\land parent(p,c)$

This means:

For all $g$ and $c$, $g$ is grandparent of $c$ if and only if there exists some $p$ such that $g$ is parent of $p$ and $p$ is parent of $c$.

This is the correct FOPL representation of the grandparent relation.

Therefore, both Statement I and Statement II are correct.