Which of the following statements is false?

The conditions given below are in the context of observing Tyndall effect in colloidal solutions:
$A$. The diameter of the colloidal particles is comparable to the wavelength of light used.
$B$. The diameter of the colloidal particles is much smaller than the wavelength of light used.
$C$. The diameter of the colloidal particles is much larger than the wavelength of light used.
$D$. The refractive indices of the dispersed phase and the dispersion medium are comparable.
$E$. The dispersed phase has a very different refractive index from the dispersion medium.
Choose the most appropriate conditions from the options given below:

The maximum coagulating power for precipitating $As_2S_3$ sol is of

In a colloidal solution,both the dispersed phase and dispersion medium are in liquid phase. What is the type of colloid?

Which principle is applicable in the purification of water using alum?

Which of the following substances forms a positively charged sol?