What are the 3 domains?

• A. Bacteria, Archaea, Eukarya
• B. Plantae, Fungi, Animalia
• C. Bacteria, Archaea, Virus
• D. Prokaryotes, Eukaryotes, Viruses

Answer: (A)

The concept being tested is how cellular organization and evolutionary relationships are grouped into domains. The three-domain system divides life into Bacteria, Archaea, and Eukarya, based on fundamental genetic differences revealed by comparing ribosomal RNA genes and other molecular traits. Bacteria and Archaea are both prokaryotes—cells that lack a nucleus—but they come from distinct lineages with different biochemistry and gene sequences. Eukarya includes all organisms with a true nucleus and internal membranes, such as plants, animals, fungi, and many protists.

Viruses aren’t included as a domain because they are acellular and do not form a universal, shared lineage like cellular life does; they depend on host cells to replicate and lack the gene set that defines cellular domains. The other options mix kingdoms within a single domain or lump noncellular entities with cellular groups, so they don’t capture the major lineage divisions that the three-domain framework reflects.