Which equation is not balanced?

A 2Mg(s) + O2(g) → 2MgO(s)

B 2Mg(NO3)2(s) → 2MgO(s) + 4NO2(g) + O2(g)

C MgO(s) + HCl(aq) → MgCl2(aq) + H2O(1)

D Mg(s) + CuSO4(aq) → MgSO4(aq) + Cu(s)

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?

How many grams of aluminum will there be in 98g of al2o3?

Great amounts of electromagnetic energy from our sun and other bodies in space travel through space. which is a logical conclusion about these electromagnetic waves? their energy must be very their frequency must be very low these waves can travel without a medium they only travel through a vacuum of space