The molar mass of o2 is 32.0 g/mol. what mass, in grams, of o2 is required to react completely with 4.00 mol of mg

The balanced equation for the reaction between Mg and O₂ is as follows
2Mg + O₂ --> 2MgO
stoichiometry between Mg and O₂ is 2:1
number of Mg reacted - 4.00 mol
if 2 mol of Mg reacts with 1 mol of O₂
then 4.00 mol of Mg requires - 1/2 x 4.00 = 2.00 mol of O₂
then the mass of O₂ required - 2.00 mol x 32.0 g/mol = 64.0 g
64.0 g of O₂ is required for the reaction 

Well to my expert knowledge and my exquisite calculations i think the the negative ion # 412 is the key to sucess

The answer is a) carbon-12