Which ion has the lowest coagulating power?

Hydrophilic sols are .......

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 colloidal sol can be prepared by the chemical oxidation method?

How does it become possible to cause artificial rain by spraying $AgI$ on the clouds?

For the coagulation of a negatively charged clay sol in water,the minimum amount of which of the following is required?