What will be the conjugate bases for the Bronsted acids: $HF$,$H_2SO_4$,and $HCO_3^-$?

The dissociation constants of two acids $HY$ and $HZ$ are $2.88 \times 10^{-4}$ and $1.8 \times 10^{-5}$ respectively. The relative strength of the acids will be :-

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:

In $NH_3$ and $PH_3$,the common property is

Which of the following cannot act as a Lewis or Bronsted acid?

Acidity of $BF_3$ can be explained on which of the following concepts?