Which of the following statements is true about the colloidal solution?

Substances like common salt, sugar and copper sulphate dissolve in water to form true solutions. The solute particles of a true solution are very small sized, i.e. less than 1 nm in diameter. On the other hand, substances like chalk powder, calcium oxide, etc. are insoluble in water. These substances, when stirred with water, form suspensions. The solute particles in suspension are large, i.e. more than 100 nm in diameter. In between these two categories, there is a third category of substance which dissolves in water or any other liquid to form mixture in which particle size is between 1–100 nm, i.e. between a true solution and a suspension, such mixtures are called colloidal solutions. Due to relatively smaller size, mixtures appear to be homogeneous, i.e. having uniform composition, but actually they are heterogeneous, i.e. particles in them are non–uniformly distributed. Although colloidal particles are small, but they are big enough to scatter light passing through them. As a result, the path of light becomes visible. This scattering of beam of light by colloidal particles is called Tyndall effect. Thus, only option 4 i.e. colloids show Tyndall effect, is correct.