How does the law of conservation of mass apply to this reaction C2H4 + O2 ----> H2O + CO2?
A. Only the oxygen needs to be balanced.
B. The law of conservation of mass has already been applied. There is an equal number of each element on both sides of the equation.
C. Each element needs to be balanced.
D. The equation needs to be balanced. There are fewer oxygen atoms in the equation than hydrogen or carbon.