During a class demonstration, a model volcano “erupts” when the teacher adds vinegar to baking soda inside the volcano. Vinegar contains acetic acid, and baking soda is sodium hydrogen carbonate. When they are combined, a reaction occurs and bubbles form. Which gas is in the bubbles, and why do the bubbles form? A. Oxygen gas forms because an acid reacts with a metal. B. Carbon dioxide gas forms because an acid reacts with a metal. C. Oxygen gas forms because an acid reacts with carbonate ions. D. Carbon dioxide gas forms because an acid reacts with carbonate ions.