Which of the following compounds is used as a fire extinguisher?

Mercury is transported in metal containers made of

Assertion : Potassium and caesium are used in photoelectric cells.
Reason : Potassium and caesium emit electrons on exposure to light.

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)

The reason why alkali metals impart color to the Bunsen burner flame is ......

Regarding the solution of alkali metals in liquid ammonia,select the incorrect statement.