Which of the following compounds is insoluble in acetic acid?

The $pH$ of a saturated solution of $Ca(OH)_{2}$ is $9$. The solubility product $(K_{sp})$ of $Ca(OH)_{2}$ is:

Find the concentration of the ion which is first precipitated at the point when the third ion starts precipitating,if $AgNO_3$ is added gradually to a solution that contains $0.1 \ M \ Cl^{-}$,$0.1 \ M \ Br^{-}$,and $0.1 \ M \ I^{-}$.
Given that:

Salt	$K_{sp}$
$AgCl$	$2 \times 10^{-10}$
$AgBr$	$5 \times 10^{-13}$
$AgI$	$9 \times 10^{-17}$

The solubility of $Al(OH)_3$ in a buffer solution at $pH = 8.0$ is [$K_{sp}$ of $Al(OH)_3 = 2.7 \times 10^{-27}$]

Solubility of $CaF_2$ in a solution of $Ca(NO_3)_2$ will be represented by the concentration term?

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Pb(AcO)_2 + H_2S \longrightarrow PbS \downarrow + 2AcOH$