Which of the following is the strongest Bronsted base?

The conjugate base of phosphorus acid is $x$. The conjugate base of oleum is $y$. What are $x$ and $y$,respectively?

The conjugate bases for $HCO_3^-$ and $NH_3$,respectively,are

Which of the following is not a Bronsted acid?

If the $pK_b$ of the fluoride ion $(F^-)$ at $25^{\circ}C$ is $10$,what is the ionization constant $(K_a)$ of hydrofluoric acid $(HF)$ at the same temperature?

Cis-butene dioic acid $\overset{K_{a_1}(-H^+)}{\longleftrightarrow} X_1^- \overset{K_{a_2}(-H^+)}{\longleftrightarrow} X_2^{2-}$
Trans-butene dioic acid $\overset{K'_{a_1}(-H^+)}{\longleftrightarrow} Y_1^- \overset{K'_{a_2}(-H^+)}{\longleftrightarrow} Y_2^{2-}$
The incorrect statement regarding the above information is: