Answer: The correct answer is no spectator ion.
Step-by-step explanation:
Spectator ions are defined as the ions which does not get involved in a chemical equation. They are found on both the sides of the chemical reaction when it is present in ionic form.
The chemical equation for the reaction of sulfuric acid and barium hydroxide is given as:

Ionic form of the above equation follows:

There are no spectator ions in the equation. So, the above reaction is the net ionic equation.
Hence, the correct answer is no spectator ion.