Measuring Zeta potential is useful in determining which property of colloidal solution?

Gelatin is a protective colloid for which of the following?

Milk is an example of a/an ...... .

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: Dissolved substances can be removed from a colloidal solution by diffusion through a parchment paper.
Reason $(R)$: Particles in a true solution cannot pass through parchment paper but the colloidal particles can pass through the parchment paper.
In the light of the above statements,choose the correct answer from the options given below.

Which one of the following is used as a disinfectant in water treatment?

At high concentration of soap in water,soap behaves as . . . . . . .