Answer:
C. The law applies, but all reactants and products must be accounted for.
Step-by-step explanation:
The law of conservation of the matter is a law in physics that states that whem a reaction takes place you can not create more matter than the matter that already exists, so in this case the mass is increasing because it is recting with the oxygen in the environment so that´s why the mass is increasing, in this case the law applies but you have to take into account all the reactants which should include the oxygen in the environment.