Solution
= Solution
Assume every morphism of $\mathcal C$ is monic. For a representable presheaf $F=\mathcal C(-,A)$, the category $(1\downarrow F)$ is the <category of elements>, equivalently the slice $\mathcal C/A$. A morphism from $f:B\to A$ to $g:C\to A$ is an $h:B\to C$ satisfying $gh=f$. Since $g$ is monic, there is at most one such $h$. Thus $(1\downarrow F)$ is a <preorder>.