1. The problem asks to evaluate the expression $$\int y \, dz + \int z \, dy$$ where both $y$ and $z$ are functions of $x$. 2. Recall the product rule for differentiation: $$d(yz) = y \, dz + z \, dy$$ where $d(yz)$ is the differential of the product $yz$. 3. Integrating both sides with respect to $x$, we get: $$\int d(yz) = \int y \, dz + \int z \, dy$$ 4. The integral of a differential $d(yz)$ is simply the function $yz$ plus a constant of integration $c$: $$yz + c = \int y \, dz + \int z \, dy$$ 5. Therefore, the expression $$\int y \, dz + \int z \, dy$$ equals $$yz + c$$. 6. The correct answer is option (c) $$yz + c$$.