Which trait distinguishes between the kingdoms of Bacteria and Archaea?
whether or not the organisms thrive in extreme conditions
whether or not the organisms thrive have a nucleus
whether or not the organisms are unicellular or multicellular
whether or not the organisms have a cell wall

I would say that the best answer is A.

Explanation:

Both Bacteria and Archaea, lack a nucleus and are unicellular. Most Archaea have a Cell wall, however there are a few exceptions, all Bacteria have a cell wall. Maybe the biggest difference between the two however, is where they thrive. Archaea live in extreme conditions, while bacteria don't. Due to this, I would say that the best answer is A, because this is the only question with a major difference in answers.