The correct option among the following is:
a.) Colloidal particles in lyophobic sols can be precipitated by electrophoresis
b.) Brownian motion in colloidal solution is faster the viscosity of the solution is very high
c.) Colloidal medicines are more effective because they have small surface area
d.) Addition of alum of water makes it unfit for drinking

Hint:. Colloids are those substances which are amorphous in nature and whose solutions are unable to pass through the membrane. It is a substance microscopically dispersed evenly throughout other substances. For example milk is an emulsion which is a colloid in which both the particles present are in liquid state.

Complete step by step answer:
Lyophobic colloids are the liquid hating colloids. Lyo means solvent and phobic means hating. When these types of colloids are mixed with a liquid which is suitable for mixing.
There is a very weak force of attraction present between the colloidal particles and the liquids and the system formed does not pass into the colloidal state readily or we can say that these are the irreversible colloids and once they are peptized they cannot be converted back into colloids.
Lyophilic sols are formed from gums, starch or proteins so they can be easily precipitated. And when a very large quantity of electrolytes are added it can lead to precipitation.
So, the correct answer is “Option A”.

Note: The colloidal particles never settle down. The size of the colloidal particle is between 1nm to 100nm. These particles are very small in size so they can not be seen through naked eyes. Colloidal particles are a type of mixture which appears to be homogeneous but it is actually a heterogeneous mixture so don’t get confused if this type of question is asked.