Combustion reactions use which element as a reactant?

Explanation:

The chemical combustion reactions use a compound called fuel (containing carbon and hydrogen atoms, example: CH4 methane) and oxygen, generating C02 (carbon dioxide) and H20 (water).

Oxygen

Explanation:

Especially hydrocarbons react with oxygen to produce carbon dioxide and water

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

i think it's letter a.