You are asked to balance the chemical equation H2 + O2 ® H2O. How many of the following ways are correct ways to balance this equation?
I. 2H2 + O2 ® 2H2O
II. H2 + O2 ® H2O
III. 4H2 + 2O2 ® 4H2O
IV. H2 + O2 ® H2O2