The correct option is D (b) and (c) above
Tyndall effect:
If a strong beam of light is passed through a colloidal sols placed in dark place, path of the beam gets illuminated. This effect is called Tyndall effect.
This effect was first observed by faraday later studied in detail by Tyndall.
This effect arises due to scattering of light by colloidal particles in all directions . Thus, scattering of light illuminates the path of beam in the colloidal dispersion.
It is used to distinguish between a colloidal and a true solution.
True solution does not show Tyndall effect but colloidal solution shows.
Salt solution and CuSO4 solutions are true solutions so they do not show Tyndall effect whereas milk and starch are colloidal solutions so they shows Tyndall effect.