Concept:Turmeric is a natural indicator. It changes color in the presence of acids or bases.Explanation:Turmeric powder is naturally yellow in color. When it comes into contact with a basic solution (like baking soda), it turns red. This color change happens because bases react with the curcumin in turmeric. Turmeric does not change color in acids. So, turmeric is used to test for bases. The change to red is specific to basic substances.Answer:A. red