Which of the following can be used to extinguish a fire caused by alkali metals?

The strongest reducing agent among the following is:

Comment on each of the following observations:
$(a)$ The mobilities of the alkali metal ions in aqueous solution are
$Li^{+} < Na^{+} < K^{+} < Rb^{+} < Cs^{+}$
$(b)$ Lithium is the only alkali metal to form a nitride directly.
$(c)$ $E^{\circ}$ for $M^{2+}_{(aq)} + 2e^{-} \longrightarrow M_{(s)}$ (where $M = Ca, Sr$ or $Ba$) is nearly constant.

The stability of peroxides and superoxides of alkali metals increases as we go down the group. Explain giving reasons.

Write the general chemical reaction that shows the dissolution of an alkali metal in liquid ammonia.

Which of the following is the strongest reducing agent?