Nick is researching why baking powder is a common baking ingredient. He learns that baking powder contains tartaric acid and sodium hydrogen carbonate. He also learns that when water is added to cake ingredients, a reaction occurs. It causes bubbles to form that make the cake rise. What gas is in the bubbles, and why do they form? A. Carbon dioxide gas forms because an acid and a carbonate react. B. Carbon dioxide gas forms because an acid and a base react. C. Hydrogen gas forms because an acid and a metal react. D. Hydrogen gas forms because an acid and a base react.