Sodium metal can be stored under

Match the following alloys in List-$I$ with their uses in List-$II$:

List-$I$ (Alloy)	List-$II$ (Use)
$A$. $Li-Pb$	$I$. In aircraft construction
$B$. $Be-Cu$	$II$. To make bearings for motor engines
$C$. $Mg-Al$	$III$. To make tetraethyl lead
$D$. $Na-Pb$	$IV$. To make high strength springs

Arrange the following compounds in the increasing order of their thermal stability. Identify the correct sequence.
$I - K_2CO_3, II - MgCO_3, III - CaCO_3, IV - BeCO_3$

The wire of a flash bulb is made of

Fluorosis disease is caused due to the reaction of ...... with excess of fluoride in the body.

Starting with sodium chloride,how would you proceed to prepare:
$(i)$ sodium metal
$(ii)$ sodium hydroxide
$(iii)$ sodium peroxide
$(iv)$ sodium carbonate?