A person found that the cake prepared by him is hard and small in size. Which ingredient has he forgotten to add that would have caused to cake to rise and become light/ Explain your answer.

Explanation

She has forgotten to add baking powder .When baking powder (sodium bicarbonate and tartaric acid mixture) is added during the preparation of cake and heated , , sodium bicarbonate reacts with tartaric acid and form carbon dioxide gas .This `CO_(2)` evolved makes the cake light and fluffy .