Final answer:
The two domains that members of the former kingdom Monera are classified under are the D) Archaea and Bacteria. These represent the two distinct groups of prokaryotic organisms.
Step-by-step explanation:
Members of what was once the kingdom Monera are now divided into two major domains called the Archaea and Bacteria. These two domains are both entirely composed of small, single-celled organisms known as prokaryotes, which lack a nucleus. While they share similarities in being made up of prokaryotic cells and often having cell walls, the cell walls of Bacteria and Archaea are made of different materials.
Specifically, bacterial cell walls contain the polysaccharide peptidoglycan. Additionally, Archaea are known to inhabit extremely harsh environments, such as hot springs and salt flats, while Bacteria can be found in more diverse and less extreme environments.
Therefore, the correct answer to the question is: Members of what was once the kingdom Monera are now divided into two major domains called the Archaea and Bacteria, which corresponds to option D.