Among $CO_3^{2-}$,$OH^{-}$,$NH_3$ and $HCO_3^{-}$,the species that acts as a Bronsted acid as well as a Bronsted base,is

Which of the following represents the correct order of increasing $pKa$ values for the given acids?

The values of dissociation constants $(K_a)$ of some acids (at $25\,^{\circ}C$) are as follows. Indicate which is the strongest acid in water:
$(A)$ $1.4 \times 10^{-2}$
$(B)$ $1.6 \times 10^{-4}$
$(C)$ $4.4 \times 10^{-10}$
$(D)$ $4.3 \times 10^{-7}$

Weak acids are partially ionised in aqueous solutions. The ionisation constants of some acids are given below. Arrange these acids in increasing order of their acid strength.

Acid Index	Acid Name and Ionisation Constant $(K_a)$
$1$	Formic acid $(HCOOH)$: $1.8 \times 10^{-4}$
$2$	Hypochlorous acid $(HClO)$: $3.0 \times 10^{-8}$
$3$	Nitrous acid $(HNO_2)$: $4.5 \times 10^{-4}$
$4$	Hydrocyanic acid $(HCN)$: $4.9 \times 10^{-10}$

Which of the following statements is true for a basic solution?

The $K_{a}$ values of $A$,$B$,and $C$ are $1.8 \times 10^{-4}$,$5 \times 10^{-10}$,and $3 \times 10^{-8}$ respectively. The correct order of their acidic strength is