I am a unicellular microorganism that lives in the hypersaline waters of Southeastern Australia. What Kingdom do I belong to?

The correct answer is - Archaea or archaebacteria.

Explanation:

Archaea is the domain and the kingdom of the single-cell prokaryotic organisms as they lack a nucleus. These organisms are present in extreme habitats such as hot springs, high saline water. These organisms can live in extremely aggressive environments which makes it a uniqe characteristic of this organism.

In the given condition the organism that lives in hypersaline water is most likely a member of the  Archaea domain or Archaebacteria kingdom as it is found in the hypersaline waters of Southeastern Australia and unicellular organisms.

I think A is the answer its hard to explain but i hope this helped.