Fourier's Law of Heat Conduction states that the rate of heat conduction through a stationary medium ($q$) is proportional to the heat transfer area ($A$) and the negative temperature gradient in the direction of heat flow ($\frac{dt}{dx}$): $q = -kA \frac{dt}{dx}$, where $k$ is the thermal conductivity of the material.

Option analysis:

• Planck's equation: Relates photon energy to frequency ($E = h\nu$) or blackbody spectral radiance.
• Stokes equation: Relates drag force on a sphere moving through a viscous fluid ($F = 6\pi\eta r v$).
• Fourier's equation: Correct, governing equation of thermal conduction.
• Continuity equation: Conservation of mass in fluid flow ($\rho A v = \text{constant}$).