Which of the following is not an acid salt?

Review the equilibrium and choose the correct statement:
$HClO_4 + H_2O \rightleftharpoons H_3O^{+} + ClO_4^-$

The acid that results when a base accepts a proton is called

The strongest Bronsted base among the following anions is

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:
$(A)$ $1.4 \times 10^{-2}$
$(B)$ $1.6 \times 10^{-4}$
$(C)$ $4.4 \times 10^{-10}$
$(D)$ $4.3 \times 10^{-7}$

At $25^{\circ} C$,$K_{a}$ of formic acid is $1.8 \times 10^{-4}$. What is the $K_{b}$ of $HCOO^{-}$?