Which of the following properties is responsible for the development of colour in colloids?

Which of the following is an example of a hydrophobic sol?

Match List-$I$ with List-$II$.

List-$I$ (Colloid Preparation Method)	List-$II$ (Chemical Reaction)
$(a)$ Hydrolysis	$(i) \; 2 AuCl_{3} + 3 HCHO + 3 H_{2}O \rightarrow 2 Au(sol) + 3 HCOOH + 6 HCl$
$(b)$ Reduction	$(ii) \; As_{2}O_{3} + 3 H_{2}S \rightarrow As_{2}S_{3}(sol) + 3 H_{2}O$
$(c)$ Oxidation	$(iii) \; SO_{2} + 2 H_{2}S \rightarrow 3 S(sol) + 2 H_{2}O$
$(d)$ Double Decomposition	$(iv) \; FeCl_{3} + 3 H_{2}O \rightarrow Fe(OH)_{3}(sol) + 3 HCl$

Choose the most appropriate answer from the options given below.

Among the following,the surfactant that will form micelles in aqueous solution at the lowest molar concentration at ambient conditions is

Assertion : Colloidal solutions are stable but colloidal particles do not settle down.
Reason : Brownian movement counters the force of gravity actively on colloidal particles.

When a substance comes in colloidal state,the surface area of the particles: