Which of the following substances is insoluble in dilute hydrochloric acid?

$A$ very dilute acidic solution of $Cd^{2+}$ and $Ni^{2+}$ gives only yellow precipitate of $CdS$ on passing $H_2S$ gas. This is due to:

At $T(K)$,$K_{sp}$ of two ionic salts $MX_2$ and $MX$ is $5 \times 10^{-13}$ and $1.6 \times 10^{-11}$ respectively. The ratio of molar solubility of $MX_2$ and $MX$ is

When solid $Pb(NO_3)_2$ is added to $1 \, L$ of $H_2SO_4$ $(1 \times 10^{-3} \, M)$ to make the concentration of $Pb(NO_3)_2$ equal to $0.002 \, M$,what will happen? $(K_{sp} \text{ of } PbSO_4 = 1.3 \times 10^{-8})$

Match the following metal sulfides with their respective solubility product $(K_{sp})$ values:

Metal sulfide	Solubility product
$A$. $PbS$	$I$. $4.0 \times 10^{-53}$
$B$. $HgS$	$II$. $8.0 \times 10^{-28}$
$C$. $MnS$	$III$. $1.6 \times 10^{-24}$
$D$. $ZnS$	$IV$. $2.5 \times 10^{-13}$

If the solubility product of $Ni(OH)_2$ is $4.0 \times 10^{-15}$, the solubility (in $mol \ L^{-1}$) is