Answer
(d) $ClO{_2}^-$ is the conjugate base in this reaction.
Work Step by Step
1. Identify the acid.
$HClO_2$ is donating a proton to $H_2O$; therefore, it is the acid of this reaction.
2. The conjugate base is what the acid becomes after losing a proton.
$HClO_2$ without a proton is $Cl{O_2}^-$. Thus, this anion is the conjugate base of the reaction.
