The strongest reducing agent among the alkali metals is

Assertion $(A)$: Alkali metals and their salts impart characteristic flame colours.
Reason $(R)$: Alkali metals have low ionization enthalpy values. So,electron excitation is possible.
The correct option among the following is

What are the common physical and chemical features of alkali metals?

Which one of the following dissolves in hot concentrated $NaOH$ solution?

Which of the following salts will produce a green flame on a $Pt$ wire?

Which of the following explains why sodium metal exhibits metallic luster?