The correct answer is (b). Litmus is an acid-base indicator, which means it changes color depending on the pH of the solution it is in. It is typically used to test whether a solution is acidic or basic. Litmus is obtained from lichens, which are a type of fungus that grows in association with algae or cyanobacteria. Lichens are found in a variety of habitats, including forests, deserts, and mountains. They are an important part of the environment, as they help to stabilize soil and provide food and shelter for other organisms.
Option (a) is incorrect because bacteria are not the source of litmus. Bacteria are single-celled organisms that are found in a variety of environments, including soil, water, and the human body. They play an important role in the environment, as they help to decompose organic matter and recycle nutrients.
Option (c) is incorrect because viruses are not the source of litmus. Viruses are tiny, infectious particles that can replicate only inside living cells. They are not considered to be living organisms, as they do not have cells or organelles. Viruses cause a variety of diseases in humans and other animals.
Option (d) is incorrect because litmus is not obtained from any of the above sources. Litmus is obtained from lichens, which are a type of fungus that grows in association with algae or cyanobacteria.