2H₂ + O₂ ⇒ 2H₂O
Conservation of mass states that
In a closed system, the masses before and after the reaction are the same
So it can be concluded
So let's see which of the several options , which one has the same number of atoms on both sides of the equation
2H₂ + O₂ ⇒ 2H₂O
H ⇒ left 4, right 4
O ⇒ left 2, right 2
so the equation is in balance and represents the Law of Conservation of
Mass