21. Archaea are also called:

a. Peptidophiles

b. Lipidophiles

c. Resistophiles

d. Reservophiles

e. Extremophiles

The correct option is e. Extremophiles

Explanation:

Archaea are prokaryotic organisms which were formerly separated from the bacteria domain.

Extremophiles can be described as organisms that have the ability to live in extreme conditions. Archaea have the ability to live in extreme environmental conditions such as a volcano vent, an extreme saline condition or extreme low-temperature conditions. Hence, archaea are also known as extremophiles. These organisms can thrive in extreme, harsh conditions which none other organisms can.