Among alkali metals,which element do you expect to be least electronegative and why?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$ :- Sodium is about $30$ times as abundant as potassium in the oceans.
Reason $R$ :- Potassium is bigger in size than sodium.
In the light of the above statements,choose the correct answer from the options given below:

Salt cake is

Which of the following gives a green colour to flame?

Match List-$I$ with List-$II$:

List-$I$ (Salt)	List-$II$ (Flame colour wavelength)
$(a)$ $LiCl$	$(i)$ $455.5 \text{ nm}$
$(b)$ $NaCl$	$(ii)$ $670.8 \text{ nm}$
$(c)$ $RbCl$	$(iii)$ $780.0 \text{ nm}$
$(d)$ $CsCl$	$(iv)$ $589.2 \text{ nm}$

Choose the correct answer from the options given below:

Sodium metal can be stored under