This is found in extreme saline conditions

The correct option is archaebacteria.

Archaebacteria are primitive, single-celled prokaryotic microorganisms that belong to the domain Archaea. They are well-known for being extremophiles, which means they possess the unique ability to survive and thrive in some of the most hostile and extreme environmental conditions on Earth, such as high temperatures, extreme pH levels, and high salt concentrations.

The specific group of archaebacteria that inhabit highly saline environments (such as salt lakes, brine pools, and salt pans) are known as halophiles.
These organisms have evolved specialized cellular features, including unique cell wall compositions and membrane lipids containing branched ether-linked chains, which help them maintain osmotic balance and prevent dehydration in hyper-saline conditions.

In contrast:
• Eubacteria (true bacteria) and Mycobacteria are typically found in more moderate, mesophilic environments.
• Cyanobacteria are photosynthetic bacteria that reside in diverse aquatic environments, but they do not exhibit the same level of extreme salt tolerance and specialized adaptation as halophilic archaebacteria.