Answer
a. Cl- ion is the conjugate base of HCl.
b. $HSO_{3}$- ion is the conjugate base of $H_{2}SO_{3}$.
c. HCOO- ion is the conjugate base of $HCHO_{2}$.
d. F- ion is the conjugate base of HF.
Work Step by Step
a. Cl- ion is the conjugate base of HCl because it can accept a hydrogen proton.
b. $HSO_{3}$- ion is the conjugate base of $H_{2}SO_{3}$ because it can accept a hydrogen proton.
c. HCOO- ion is the conjugate base of $HCHO_{2}$ because it can accept a hydrogen proton.
d. F- ion is the conjugate base of HF because it can accept a hydrogen proton.