Answer: B.combustion
Step-by-step explanation:
Synthesis reaction is a chemical reaction in which two reactants are combining to form one product.
Example:
Combustion is a type of chemical reaction in which fuel is reacted with oxygen to form carbon dioxide and water.
Example:

Electrolytic is a chemical reaction in which decomposition is carried by use of electric current.
Decomposition is a type of chemical reaction in which one reactant gives two or more than two products.
Example:

Thus
is combustion reaction.