The following reaction shows the production of hydrogen gas from water. this chemical reaction should be classified as
2 h2o 2h2 + o2
synthesis
decomposition
single replacement
double displacement
neutralization

B. Decomposition

Explanation:

Decomposition is the type of reaction in which a compound is broken into smaller  compounds or broken into its elements

Synthesis is just opposite to decomposition reaction, Elements combine to form a compound

Single replacement reactions in which replacement takes place at a single place

Double replacement reactions in which replacement occurs two places

Neutralization reaction is the reaction between an acid and a base to form salt and water

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