$0.1 \ M$ solution of which of the following has almost unity degree of dissociation?

For a concentrated solution of a weak electrolyte ($K_{eq} = $ equilibrium constant) $A_2B_3$ of concentration '$c$',the degree of dissociation '$\alpha$' is

Estimate the approximate $pK_a$ of $0.5 \ M$ $CH_3COOH$. Degree of dissociation (ionisation) is $0.15$ $(\log 1.32 = 0.12)$.

Which of the following absorbs oxygen rapidly?

Statement $A$: Addition of $NH_4OH$ in the presence of excess $NH_4Cl$ to an aqueous solution of $BaCl_2$ results in the precipitation of $Ba(OH)_2$.
Reason $B$: $Ba(OH)_2$ is insoluble in water.

At $27^{\circ} C$,the degree of dissociation of $HA$ (weak acid) in $0.5 \ M$ of its solution is $1 \%$. The concentrations of $H_3O^{+}$,$A^{-}$,and $HA$ at equilibrium (in $mol \ L^{-1}$) are respectively