This reaction uses a catalyst to increase the rate of the reaction. The catalyst is a metal oxide.
Which is the most likely metal in the metal oxide catalyst? Use the periodic table.

The industrial process for making sulfuric acid is called the Contact Process. The key stage is the oxidation of sulfur dioxide to sulfur trioxide: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g). This reaction is slow, so a catalyst is needed to achieve a reasonable rate at the compromise temperature of 450°C. The catalyst used is vanadium(V) oxide, V₂O₅. Vanadium (V) is a transition metal. Transition metals and their compounds are often effective catalysts because they have variable oxidation states, which allows them to facilitate the reaction by providing an alternative reaction pathway with a lower activation energy. The other options are main group metals (Aluminium, Barium, Potassium) whose compounds are not used as catalysts for this reaction.