Given the function $w = f(x, y, z)$, where
$x = g(r, \theta)$, $y = h(r, \theta)$, $z = p(r, \theta)$,
which of the following is equal to $\frac{\partial w}{\partial r}$?
$\frac{\partial w}{\partial x}\frac{\partial x}{\partial r} + \frac{\partial w}{\partial y}\frac{\partial y}{\partial r}$
$\frac{\partial w}{\partial x}\frac{\partial x}{\partial r} + \frac{\partial w}{\partial y}\frac{\partial y}{\partial r} + \frac{\partial w}{\partial z}\frac{\partial z}{\partial r}$
$\frac{\partial w}{\partial x}\frac{\partial x}{\partial r} + \frac{\partial w}{\partial y}\frac{\partial y}{\partial r} + \frac{\partial w}{\partial z}\frac{\partial z}{\partial r} + \frac{\partial w}{\partial \theta}\frac{\partial \theta}{\partial r}$
