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.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products