Ireally need ! no one has me! will give brainliest, , andif you are good at science and hurry ! how does the law of conservation of mass apply to this reaction: c2h4 + 3o2 --> 2h2o + 2co2? a. only the oxygen needs to be balanced b. the equation needs to be balanced. there are fewer oxygen atoms in the equation than hydrogen and carbon c. the law of conservation of mass has already been applied d. each element needs to be balanced