Question

What is an indicator?Name the acid ,or base indicate ectracted from lichen.

Answer 1

Indicator is a thing that is used to detect whether the substance is basically or acidic in nature

Answer 2

A bioindicator is any species or group of species whose function, population, or status can reveal the qualitative status of the environment.
Litmus, a natural dye is extracted from lichen.

Red litmus changes to blue in a basic solution whereas blue litmus changes to red in acidic medium.

Hope it helps