Which of the following reacts with water with the highest rate?

Magnesium is burnt in the air to form $A$ and $B$. When $B$ is hydrolyzed,$C$ and $D$ are formed. $D$ is the reactant in the manufacture of nitric acid by Ostwald's process. What is $C$?

Which of the following elements forms a superoxide when it reacts with oxygen?

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

List-$I$	List-$II$
$(a)$ $Li$	$(i)$ Poor water solubility of $I^{-}$ salt
$(b)$ $Na$	$(ii)$ Most abundant element in cell fluid
$(c)$ $K$	$(iii)$ Bicarbonate salt used in fire extinguisher
$(d)$ $Cs$	$(iv)$ Carbonate salt decomposes easily on heating

Choose the correct answer from the options given below :

The properties of $Li$ are similar to those of $Mg$. What is the reason for this?

The correct order of hydration enthalpies of alkali metal ions is