Preparation of Lyophobic sols by chemical method involves

Colloidal solution of arsenious sulphide can be prepared by:

The gold numbers of $A, B, C$ and $D$ are $0.04, 0.002, 10$ and $25$ respectively. What is the order of their protective power?

Which of the following statements is true for a lyophobic sol?

Which one of the following is a hydrophilic colloidal sol?

$100 \ mL$ of $0.0018\%(w/v)$ solution of $Cl^{-}$ ion was the minimum concentration of $Cl^{-}$ required to precipitate a negative sol in one $h$. The coagulating value of $Cl^{-}$ ion is $.......$ (Nearest integer).