Substances whose odour changes in acidic or basic media are called-

Correct option is C

The correct answer is (c) Olfactory indicators.
· Olfactory indicators are substances whose smell or odor changes in response to acidic or basic environments.
· Common olfactory indicators include substances like vanilla extract, onion, and clove oil. In an acidic medium, these indicators retain their original smell, while in a basic medium, the smell changes or disappears.
Information Booster:
· Acidic indicators: These are substances that show a distinct color change only in acidic conditions. However, they are not typically used to detect odors.
· Basic indicators: These indicators are more specific to color changes in basic solutions.
· Litmus: A common example of a color-based indicator that turns red in acidic solutions and blue in basic solutions, but it does not change odor.
· Phenolphthalein: Another indicator that is colorless in acidic solutions and turns pink in basic solutions.