Identifying base in a chemical equation According to the Brønsted Lowry principle, "base" is a proton acceptor. I've tried to apply this idea to every choice as you can see these red circles in each equation below, but they are all loses protons, aren't they? How could it be a base?



However, if I choose water in a blue circle, I will get the underlined substance as a base for both choice B and C instead. Also, if you have a look at other substances involve in equation B and C, they do support the assumption that they act as acids that involved in donating protons. Hence, both B and C are correct. But the solution said the correct answer is C.
I would write down the half equations for each reaction:
A

$\ce{ HNO3 + H+ -&gt; H2NO3+ }$ (Base)
$\ce{H2SO4 -&gt; HSO4- + H+}$  (Acid)

B

$\ce{  HSiO3- -&gt; SiO2 + OH- }$  (Base)
$\ce{HCN  -&gt; CN- + H+ }$ (Acid)

C

$\ce{HNO2 -&gt; NO2- + H+ }$ (Acid)
$\ce{HCO3- -&gt; CO2 + OH- }$(Base)

D

$\ce{C6H5O- + H+ -&gt; C6H5OH }$ (Base)
$\ce{CH2ClCO2H -&gt; CH2ClCO2- + H+ }$(Acid)