the formation of bubbles a reduction in total mass the disappearance of atoms an increase in the number of atoms
I gave my students this multiple choice question: Students combined baking soda and vinegar to demonstrate a chemical reaction. What indicates that a chemical reaction occurred?

Only one answer is correct among these 4 choices:
- the formation of bubbles
- a reduction in total mass
- the disappearance of atoms
- an increase in the number of atoms

Could you tell me which one is correct?

the formation of bubbles