Final answer:
The three domains of life are Bacteria, Eukaryota, and Archaea (option b). Archaea are single-celled organisms without a nucleus and, along with Bacteria, are considered prokaryotes. Eukarya includes more complex organisms with a nucleus.
Step-by-step explanation:
The three domains of life are Bacteria, Eukaryota, and Archaea. The answer to the student's question is Archaea, which is option b. This domain consists of single-celled organisms that lack a nucleus, just like bacteria. However, archaea are genetically and biochemically distinct from bacteria and are known to inhabit extreme environments. Together with Eukarya, they represent the three broad categories of life based on cellular organization and genetic makeup. Eukarya includes organisms with cells that contain a nucleus, such as animals, plants, fungi, and protists.
It is important to note that the concept of these three domains supplants the older Five Kingdoms system. In addition, it's worth remembering that the Archaea and Bacteria are both prokaryotes, which means they lack membrane-bound organelles like a nucleus. On the other hand, the Eukarya are eukaryotes, organisms with more complex cells that possess a nucleus. Understanding these domains is essential for comprehending the tree of life and the evolutionary relationships among different life forms.