Answer: 1 - They live in extreme environmental conditions
Explanation: Archea is one of the three domains of life along with Bacteria and Eukarya and exhibit several unusual characteristics compared to other organisms. Here are a few notable aspects:
Archea are known for their ability to thrive in extreme environment including high temperature (thermophiles), high salinity (halophiles) ,high acidity (acidophiles) and even deep sea hydrothermal vents. Some archaea can survive in temperature above the boiling point of water or in highly acidic conditions which makes them unique among all known life forms. The cell wall composition of archaea are distinct from both bacteria and eukaryotes. Most archaea lack peptidoglycan , a key component of bacterial cell walls. Instead they possess a unique cell wall composition.