Molar mass of N = 14 g/mol
Molar mass of O2 = 32 g/mol
Adding both masses = 46 g/mol
Actual molar mass/ Empirical molar mass = 138.02 / 46 = 3
Now multiplying this co effecient with empirical fomula NO2 = 3(NO2)
= N3O6
So according to above explanation,
D) N3O6, is the correct answer.