greater than the mass of the carbon plus the mass of the oxygen equal to the mass of the carbon plus the mass of the oxygen equal to the mass of the carbon less than the mass of the carbon
I gave my students this multiple choice question: When carbon and oxygen combine chemically, the mass of the product is

Only one answer is correct among these 4 choices:
- greater than the mass of the carbon plus the mass of the oxygen
- equal to the mass of the carbon plus the mass of the oxygen
- equal to the mass of the carbon
- less than the mass of the carbon

Could you tell me which one is correct?

equal to the mass of the carbon plus the mass of the oxygen