What is the classification for this reaction? so3 (g) + h2o (l) → h2so4 (aq)?

There are six common types of reactions:

1. Combination
2. Decomposition
3. Single Displacement
4. Double Displacement
5. Combustion
6. Redox

The reaction: SO₃₍g₎ + H₂O₍l₎ → H₂SO₄₍aq₎ is classified as a combination reaction. This is because for combination reactions, two (or more) reactants form a single product. On the other hand, decomposition reactions involve a single reactant breaking down into two or more simpler substances. Displacement reactions involve a more active element displacing a less active element from a compound. Meanwhile, combustion reactions involve a carbon-containing compound reacting with oxygen to form carbon dioxide and water. Redox reactions then involve exchange of electrons between species.  

Where are the following questions

They are all solids.