Which of the following can form a colloidal sol with water?

Choose the correct reason$(s)$ for the stability of the lyophobic colloidal particles.
$(A)$ Preferential adsorption of ions on their surface from the solution.
$(B)$ Preferential adsorption of solvent on their surface from the solution.
$(C)$ Attraction between different particles having opposite charges on their surface.
$(D)$ Potential difference between the fixed layer and the diffused layer of opposite charges around the colloidal particles.

Which of the following is an emulsion?

Which of the following is a water-in-oil $(W/O)$ type of emulsion?

The size of particles in suspension,true solution and colloidal solution varies in the order:

This equation represents the preparation of gold sol: $2 AuCl_3 + 3 HCHO + 3 H_2 O \rightarrow 2 Au + 3 HCOOH + 6 HCl$. What type of reaction is this?