Which of the following is the net ionic equation for the reaction that occurs during the titration of nitrous acid with potassium hydroxide?
a) HNO_2 + K^+ OH^- --> KNO_2 + H_2O
b) HNO_2 + H_2O --> NO_2^- + H_3O^+
c) HNO_2 + KOH -->+ + NO_2^- + H_2O
d) HNO_3 + OH --> NO_2^- + H_2O
e) H^+ + OH^- --> H_2O