Consider the following pairs: 

  1. Stoneflies→ indicate high oxygen content in water
  2. Mosses→ indicate acidic soil
  3. Greasewood→ indicates saline soil

   Which of the above is/are correct?

Answer: [D] 1, 2 & 3

All of the above are correct
An indicator species is any biological species that defines a trait or characteristics of the environment. Indicator species are sensitive to environmental changes and can act as early warning regarding adverse environmental changes in particular area.

This question is a part of GKToday's Integrated IAS General Studies Module