Which coloured light scatters least by fog and smoke?

Fog and smoke scatters those wavelengths of light whose wavelength is far shorter to the size of fog and smoke particles.

According to the Rayleigh Law of scattering, the amount of scattering is proportional to $\frac{1}{{\lambda }^4}$

And, since red light has largest wavelength among all visible parts of light, it is scattered the least.

Answer-(D)