= Solution
{c}
For a bounded region $V\subset\mathbb R^3$ with piecewise smooth boundary, suppose $\mathbf F$ is a <continuously differentiable vector field> on an open neighbourhood of its <closure>. The <divergence theorem>, with outward <unit normal vector> $\mathbf n$, is
$$
\boxed{\iiint_V\nabla\cdot\mathbf F\,dV
=\iint_{\partial V}\mathbf F\cdot\mathbf n\,dS.}
$$
The <surface integral> measures total outward <flux>. Edges and isolated vertices have zero <surface area> and do not affect the <integral>.
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