Which of the following compounds accepts a proton from a water molecule according to the Bronsted-Lowry theory?

Which of the following species can act as both a Bronsted acid and a Bronsted base?

The nitrating mixture contains concentrated $H_2SO_4$ and concentrated $HNO_3$. In this mixture,$HNO_3$ acts as a:

The total number of diprotic acids among the following is:
$H_3PO_4, H_2SO_4, H_3PO_3, H_2CO_3, H_2S_2O_7, H_3BO_3, H_3PO_2, H_2CrO_4, H_2SO_3$

Phosphoric acid ionizes in three steps with their ionization constant values $K_{a_1}, K_{a_2}$ and $K_{a_3}$ respectively,while $K$ is the overall ionization constant. Which of the following statements are true?
$A.$ $\log K = \log K_{a_1} + \log K_{a_2} + \log K_{a_3}$
$B.$ $H_3PO_4$ is a stronger acid than $H_2PO_4^{-}$ and $HPO_4^{2-}$
$C.$ $K_{a_1} > K_{a_2} > K_{a_3}$
$D.$ $K_{a_1} = \frac{K_{a_3} + K_{a_2}}{2}$
Choose the correct answer from the options given below

The $pK_a$ values in $H_2O$ of picric acid,acetic acid,and phenol are in the order: