An emulsion is a colloidal solution containing ........

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Finest gold is red in colour,as the size of the particles increases,it appears purple then blue and finally gold.
Assertion $R$: The colour of the colloidal solution depends on the wavelength of light scattered by the dispersed particles.
In the light of the above statements,choose the most appropriate answer from the options given below:

In which of the following,the sol is not correctly matched with respect to its charge?
$I$. $Al_2O_3 \cdot xH_2O$ sol; $+ve$ sol
$II$. Starch sol; $+ve$ sol
$III$. $TiO_2$ sol; $-ve$ sol
$IV$. Methylene blue sol; $+ve$ sol
The correct answer is

Which of the following is lyophobic in nature?

As per the Hardy-Schulze rule,the flocculation values of the following electrolytes for a ferric hydroxide sol are in the order:

On adding a few drops of dilute $HCl$ or $FeCl_3$ to freshly precipitated ferric hydroxide,a red-coloured colloidal solution is obtained. This phenomenon is called: