Which one of the alkali metals forms only the normal oxide,$M_2O$,on heating in air?

Assertion : Magnesium continues to burn in nitric oxide.
Reason : During burning heat evolved does not decompose $NO$.

Two elements $A$ and $B$ have similar chemical properties. They do not form solid hydrogencarbonates,but react with nitrogen to form nitrides. $A$ and $B,$ respectively,are :

Which of the following sets represents the alkali metals?

Identify $A$ to $E$ in the following reactions:
$\underset{\text{Alkali metals}}{\mathop{A}}\,+N_2$ $\xrightarrow{\Delta }B$ $\xrightarrow{H_2O}C+D$
$C+HCl\rightarrow E$
(Where $D$ is $NH_3$ and $E$ is a salt,and $C$ is a base)

How is $NaCl$ prepared from brine (sea water)?