Answer: Nucleus
Step-by-step explanation:
The presence of Nucleus in the eukaryotic cell shows that the cell is an eukaryotic cell. The Nucleus is the genetic material found in all the eukaryotic cell which helps in the transfer of the genetic information from one generation to another.
This is a characteristic feature of eukaryotes. It is not found in the prokaryotes. They lack nucleus and their genetic material is dissolved in the cytoplasm.
Hence, the correct answer is Nucleus.