All organisms that do not fit into plant, fungi, and animal kingdoms but have a nucleus are:

• A. Bacteria
• B. Protists
• C. Fungi
• D. Plants

Answer: (B)

Think about the distinction between organisms with a nucleus and those without, and how living things are grouped. Organisms that have a nucleus are eukaryotes, but not all eukaryotes belong to the plant, animal, or fungal kingdoms. The group that fits here is protists—a diverse collection of mostly single-celled or simple multicellular eukaryotes that don’t fall into the other three kingdoms. Protists include a wide range of organisms, from algae that photosynthesize to amoebas that engulf food, so they’re united by having a nucleus but not by belonging to plants, animals, or fungi. In contrast, bacteria are prokaryotes and lack a nucleus, so they don’t fit this description. Plants, animals, and fungi are separate kingdoms with their own distinct characteristics, making protists the best match for organisms with a nucleus that aren’t in those three kingdoms.