Which of the following fluoro-compounds is most likely to behave as a Lewis base?

Which of the following statements about ${{\mathrm{HCO}}_3}^{-}$ are correct?

$1$. It is a Bronsted acid.

$2$. It can ionize in water to form ${{\mathrm{CO}}_3}^{2-}\left(\mathrm{aq}\right)$.

$3$. It does not exist in aqueous solution.

$4$. It is a Bronsted base.

Select the correct answer using the codes given below.

The strongest conjugate base is

In aqueous solution, the ionization constants for carbonic acid are ${\mathrm{K}}_1=4.2\times {10}^{-7}$ and ${\mathrm{K}}_2=4.8\times {10}^{-11}$. Select the correct statement for a saturated $0.034 \mathrm{M}$solution of the carbonic acid.