Answer:
This question is incomplete as it does not contain any provided information. The information is as follows:
Number of cells: Unicellular
Cell type: Prokaryotic
Location found: Underwater volcano
The answer is Archaea
Explanation:
Living organisms has been classified into a large group of three called DOMAIN consisting of Bacteria, Eukarya and Archaea. The major basis of this classification is the possession or not of a membrane-bound nucleus.
Domains Bacteria and Archaea do not possess a membrane-bound nucleus and hence, are PROKARYOTIC. However, in addition to being prokaryotic, Domain Archaea members are unicellular (single-celled) and are found in locations with harsh environmental conditions e.g volcano.
Therefore, an organism with a PROKARYOTIC cell type, UNICELLULAR number of cells and found in an UNDERWATER VOLCANO will belong to the domain ARCHAEA.