The reaction 2Mg(s) + O2(g) --> 2MgO(s) is a Group of answer choices
double-replacement reaction.
decomposition reaction.
synthesis reaction.
single-replacement reaction.

Double-Replacement Reaction

Explanation:

Mg is Oxidized, and O2 is the cause of the oxidation, hence the Oxidizing agent.  That means that O2 is Reduced and Mg is the cause naming it the Reducing agent.

OIL - RIG   Oxidation is Loss-Reduction is Gain

the energy to form plasma comes from heat or electricity in the atmosphere!

sunny~ ☺