Answer: The correct answer is-
Archaea.
According to the three domain system of classification ( proposed by Carl Woese), Archaea is a domain of prokaryotic organisms ( that is lacking nucleus and subcellular compartements) that includes primitive forms of bacteria.
These organisms are adapted to survive under extremely harsh environmental conditions ( therefore also called extremophiles) such as hotsprings, boiling mud surrounding volcanoes.
Example- Methanogens, thermophiles, and halophiles.
