Which complex is most stable? Where $k_d =$ Dissociation constant.

Which of the following complexes has the highest $C-O$ bond length?

The colour of $CoCl_3 \cdot 5NH_3 \cdot H_2O$ is

Which one of the following will give a white precipitate with $AgNO_3$ in aqueous medium?

Copper sulphate solution reacts with $KCN$ to give

Choose the correct statements from the following:
$A$. Ethane$-1, 2-$diamine is a chelating ligand.
$B$. Metallic aluminium is produced by electrolysis of aluminium oxide in the presence of cryolite.
$C$. Cyanide ion is used as a ligand for the leaching of silver.
$D$. Phosphine acts as a ligand in Wilkinson's catalyst.
$E$. The stability constants of $Ca^{2+}$ and $Mg^{2+}$ are similar with $EDTA$ complexes.
Choose the correct answer from the options given below: