Which one of the following is not a colloid?

Identify a zero dimensional nano structure from the following.

Match the following:

List-$I$ (Sol)	List-$II$ (Method of preparation)
$A$. $As_2S_3$	$IV$. Double decomposition
$B$. $Au$	$I$. Bredig's arc method
$C$. $S$	$II$. Oxidation
$D$. $Fe(OH)_3$	$III$. Hydrolysis

The correct answer is:

Coagulating value of electrolytes $AlCl_3$ and $NaCl$ for $As_2S_3$ are $0.09$ and $50.04$ respectively. The coagulating power of $AlCl_3$ is $x$ times the coagulating power of $NaCl$. The value of $x$ is $.......$.

Equal volumes of two $AgI$ sols are mixed together. The first sol is obtained by adding $AgNO_3$ to a slight excess of $KI$,and the second sol is obtained by adding $KI$ to a slight excess of $AgNO_3$. What happens when they are mixed?

Which of the following colloidal solutions cannot be prepared by Bredig's arc method?