Which of the following are likely to be present in deep sea water

The correct option is archaebacteria.

Archaebacteria are a group of primitive, single-celled microorganisms that are known for their ability to survive in some of the most extreme environments on Earth, such as deep-sea hydrothermal vents, hot springs, and hypersaline lakes. These organisms are classified as extremophiles due to their specialized cell wall structure and unique lipid membranes, which protect them from extreme heat, high pressure, and highly acidic or alkaline conditions. In contrast, eubacteria, saprophytic fungi, and blue-green algae (cyanobacteria, which require sunlight for photosynthesis) are generally unable to thrive in the harsh, high-pressure, and lightless environments of the deep sea.