Which domain describes organisms with a nucleus?

• A. Prokaryotes
• B. Eukaryotes
• C. Archaea
• D. Viruses

Answer: (B)

The main idea is that having a nucleus is a defining feature of certain cells. Organisms whose cells contain a membrane-bound nucleus fall into the group known as eukaryotes. In these cells, DNA is housed inside the nucleus, and there are other membrane-bound organelles that support complex cellular functions. This contrasts with prokaryotes, whose cells lack a true nucleus and have simpler internal organization. Viruses aren’t cells at all and don’t have a nucleus or cellular compartments, so they don’t fit into the cellular categories. Therefore, the correct description is eukaryotes, the group whose cells do possess a nucleus.