Answer
(a) $N{O_2}^-$
(b) $HS{O_4}^-$
(c) $HS^-$
(d) $CN^- $
(e) $HCOO^-$
Work Step by Step
A conjugate base is the result of taking a proton from the acid, therefore, all we need to do is:
1. Take one of the $H's$ out
Ex: - $HNO_2$ -> $NO_2$
2. Subtract 1 from the charge:
Ex - $NO_2$ -> $N{O_2}^-$
