Which of the following behaves as both a Lewis base and a Bronsted base?

In the following reaction:
$[Al(H_2O)_6]^{+3} + HCO_3^{-} \rightleftarrows [Al(H_2O)_5OH]^{+2} + H_2CO_3$
$(A)\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad(B)\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad(C)\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad(D)$
Which species behave as Bronsted-Lowry acids?

Observe the following species: $AlCl_3, NH_3, H^{+}, Co^{3+}, OH^{-}, Mg^{2+}, BF_3, Cl^{-}$. How many Lewis acids are present in the above list?

Which of the following compounds are diprotic?

The $pK_a$ value of the strongest acid among the following is:

Of the following compounds, which one is the strongest Bronsted acid in an aqueous solution?