Answer:
Combination reaction
Step-by-step explanation:
In Chemistry, elements and compounds are involved in a process called chemical reactions, which are of different types namely: combination, decomposition, double replacement, combustion etc. A combination reaction is that reaction in which two or more substances called the REACTANTS combine together to form a single new substance called the PRODUCT.
In this case, a reaction is depicted as follows:
2SO2(g) + O2(g) --> 2SO3(g)
In this reaction, compound SO2 combines chemically with element O2 to form a single new compound SO3. Hence, this is a type of COMBINATION REACTION.