Correct answer is .
Phosphoric acid is a polyprotic acid having 3 acidic hyrdogen therefore it will have 3 pka values.
The equations for the release of acidic hydrogen can be written as:
From the pka values we can judge the idea of pH as using Henderson-Hasselbalch Equation, we get the relation between pH and pka.
Using the following equation, relation of pH and pka is
Using this equation, we can find that the equation having pka= 2. 14 is closest to the pH=3.2 so the ionic form in this equation will be dominant at the same pH.
Therefore at pH=3.2 the ionic form of
is dominant.