Which of the following acts as a Brønsted base?

$A$ salt of sulphurous acid is called

The conjugate acid of $NH_2^-$ is

Which of the following is a Lewis acid but not a Bronsted acid?

The dissociation constants $(K_a)$ of four acids are given below. Which of these is the strongest acid?

The ionization constants of two bases $AOH$ and $BOH$ are $K_{b1}$ and $K_{b2}$ respectively. Their relationship is $pK_{b1} < pK_{b2}$. Which of the following does not represent the base with the highest $pH$?