Which of the following electronic configurations in the outermost shell is characteristic of alkali metals?

Hydroxide of which alkali metal is used in the manufacture of soft soap?

Why are alkali metals highly reactive?

Which of the following is insoluble in water?

Identify the correct statements about alkali metals.
$A$. The order of standard reduction potential $(M^{+} \mid M)$ for alkali metal ions is $Na > Rb > Li$.
$B$. $CsI$ is highly soluble in water.
$C$. Lithium carbonate is highly stable to heat.
$D$. Potassium dissolved in concentrated liquid ammonia is blue in colour and paramagnetic.
$E$. All the alkali metal hydrides are ionic solids.
Choose the correct answer from the options given below.

Assertion : $K$,$Rb$ and $Cs$ (all belonging to group $1$) can also form superoxides.
Reason : The ionic radii of $K$,$Rb$ and $Cs$ show the following trend $Cs^{+} < Rb^{+} < K^{+}$.