Question

Bioindicators are used for knowing—
A. Minerals
B. Oxygen demand
C. Air pollution
D. All of the above

Answer 1

Hint: These indicators can be seen in various climates. Every category has its own indicators for the environment. These control all the organisms and nature itself.

Complete answer:
Bioindicators are those species which can reveal the status of the quality of the air of the environment. These are capable to describe the role of various pollutants and the time from when the change of events had occurred. These species are copepods and small water body crustaceans. These indicators describe the amount of changes in the quality of the air. These can also explain the intensity of the effects being caused.
Assessing the sterility of the environment is also a role of bioindicators.
Strains like bacillus and geobacillus can be used to test the environment.
There are also some plant indicators present in nature. These include mosses, lichens, tree bark, pockets of the bark, leaves etc.
Lichens can be seen on rocks and tree trunks. Absence of the lichens from the forest indicate an unhealthy environment such as presence of increased sulfur based pollutants and nitrogen oxides.
As a result of this the animal species can also suffer. Decrease in the plants can lead to decreased count of the herbivores.
In the case of microbes it has been seen that when exposed to cadmium and benzene there is production of different types of proteins in their body.

So the correct answer is D i.e all of the above.

Note: Assessing the sterility of the environment is also a role of bioindicators.
Strains like bacillus and geobacillus can be used to test the environment. Plant indicators include mosses, lichens, tree bark, pockets of the bark, leaves etc.