The pressure $\frac{\partial p}{\partial z}$ in fluid at rest due to gravity is given by

Question

If z is vertically upwards, $\rho$ is the density and g gravitational  acceleration (see figure), then the pressure $\frac{\partial p}{\partial z}$ in fluid at rest due to gravity is given by

(a) $\rho gz^{2}/2$                     (b) $-\rho g$

(c) $-\rho gz$                        (d) $\rho g/z$