Answer
a. Nitrite is $NO_2^-$
b. Sulfite is $SO_3^{2-}$
c. Hydroxide is $OH^-$
d. Acetate is $C_2H_3O_2^-$
Work Step by Step
You can find the answers to this question on page 197, table 6.7 'Names and Formulas of Some Common Polyatomic Ions'. Doing this, we find:
a. Nitrite is $NO_2^-$
b. Sulfite is $SO_3^{2-}$
c. Hydroxide is $OH^-$
d. Acetate is $C_2H_3O_2^-$
