How many of the following are diprotic acids? Citric acid, Chromic acid, Oxalic acid, Pyrosulfuric acid, Sulfurous acid

Match the following acids in List-$I$ with their respective acid dissociation constants $(K_a)$ in List-$II$:

List-$I$ (Acid)	List-$II$ $(K_a)$
$A$. Phenol	$I$. $1 \times 10^{-13}$
$B$. Benzoic acid	$II$. $3.0 \times 10^{-8}$
$C$. $HClO$	$III$. $1.0 \times 10^{-10}$
$D$. $CH_3COOH$	$IV$. $6.5 \times 10^{-5}$
	$V$. $1.75 \times 10^{-5}$

The correct match is:

The strongest Bronsted base among the following anions is:

For the species $HSO_4^{-}$ and $NH_3$,their conjugate acids respectively are

Which of the following is the strongest Lewis base?

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R:$
Assertion $A :$ The amphoteric nature of water is explained by using Lewis acid/base concept.
Reason $R :$ Water acts as an acid with $NH_{3}$ and as a base with $H_{2}S$.
In the light of the above statements,choose the correct answer from the options given below: