Final answer:
The presence of a membrane-enclosed nucleus is a characteristic of eukaryotic cells.
Step-by-step explanation:
The presence of a membrane-enclosed nucleus is a characteristic of eukaryotic cells. Eukaryotic cells are found in organisms within the domain Eukarya, which includes plants, animals, fungi, and protists. The nucleus contains the cell's DNA and is surrounded by a double membrane called the nuclear envelope. This membrane separates the genetic material from the rest of the cell and allows for compartmentalization of cellular functions.