At 25° C, the dissociation constant of a weak monoprotic acid $HA\left({\mathit{K}}_a\right)$ is numerically equal to the dissociation constant of its conjugate base $A^{-}\mathit{ }\left(K_b\right)$ Which of the following statement(s) is are correct?

The pH of 0.1 M aqueous solution of the conjugate base $\left(A^{-}\right)$ is 10.0.

The pH of 0.1 M aqueous solution of the acid, HA, is 4.0.

The pH of an aqueous solution containing$0.1 \mathrm{M} -\mathrm{HA}$ and $0.01$  $\mathrm{M}-\mathrm{HCl}$ is $2.0.$

The dissociation constant of the acid, HA, is ${10}^{-7}\text{ at }{25}^{\circ }\mathrm{C}$