The velocity of neutrons in a nuclear reactor is slowed down by

Match the following:

List-$I$ (Reactions)	List-$II$ (Methods)
$A$. $Mg(HCO_3)_2 \rightarrow Mg(OH)_2 \downarrow + 2 CO_2 \uparrow$	$I$. Clark's method
$B$. $M^{2+} + Na_4P_6O_{18}^{2-} \rightarrow [Na_2MP_6O_{18}]^{2-} + 2 Na^{+}$	$II$. Ion exchange method
$C$. $Ca(HCO_3)_2 + Ca(OH)_2 \rightarrow 2 CaCO_3 + 2 H_2O$	$III$. Boiling
$D$. $2 NaZ + Ca^{2+}_{(aq)} \rightarrow 2 Na^{+} + CaZ_2$ ($Z$ = Zeolite)	$IV$. Calgon's method

Clark's method is used to

The surface tension of which of the following liquids is maximum?

Which of the following is/are considered hard water?

Identify the reactions in which $H_2O$ is oxidised:
$I$. Photosynthesis
$II$. Reaction of $H_2O$ with fluorine
$III$. Reaction of $H_2O$ with hydrogen
$IV$. Reaction of $H_2O$ with $P_4O_{10}$
The correct answer is