Sodium gives blue colour with $NH_3$ solution,this blue colour is due to

$CO_2 + NH_3 + H_2O \to X$
$X + NaCl \to Y + NH_4Cl$
$2Y \xrightarrow{\Delta} Z + H_2O + CO_2$. '$Z$' is

How is magnesium obtained from the following?

Match column $-I$ with column $-II$ :

Column $-I$	Column $-II$
$(a)$ Borax	$(p)$ $NaCl$
$(b)$ Carnallite	$(q)$ $KCl$
$(c)$ Rock salt	$(r)$ $KCl.MgCl_2.6H_2O$
$(d)$ Silvine	$(s)$ $Na_2B_4O_7.10H_2O$

The correct statement$(s)$ among $I$ to $III$ with respect to potassium ions that are abundant within the cell fluids is/are :
$I.$ They activate many enzymes
$II.$ They participate in the oxidation of glucose to produce $ATP$
$III.$ Along with sodium ions,they are responsible for the transmission of nerve signals

Calcium is obtained by