The value of colligative property of a solution depends upon the number of particles present in solution. Value of colligative property increase with the increase in the number of particles. So it does not depends on other factors.

Therefore options (i),(ii) and (iii) are wrong.

Now, in true solution, the size of particle is very small compared to the colloidal particles (1-1000 nm). So for the same concentration of solution, the number of particles in colloidal particles is much less than that of true solution particles. So option (iv) is correct.