Which of the following has the lowest melting point?

Which of the following does not illustrate the anomalous properties of lithium?

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

List-$I$	List-$II$
$(a)$ $Li$	$(i)$ photoelectric cell
$(b)$ $Na$	$(ii)$ absorbent of $CO_{2}$
$(c)$ $K$	$(iii)$ coolant in fast breeder nuclear reactor
$(d)$ $Cs$	$(iv)$ treatment of cancer
	$(v)$ bearings for motor engines

Choose the correct answer from the options given below:

Explain the biological importance of sodium and potassium.

Identify the correct order of standard enthalpy of formation of sodium halides.

State the reasons for the following:
$(a)$ Why is a solution of $Na_{2}CO_{3}$ alkaline?
$(b)$ Why are alkali metals prepared by the electrolysis of their fused chlorides?
$(c)$ Why is sodium found to be more useful than potassium in biological systems?