For your first question, the organelle that you would ONLY find in a eukaryotic cell is mitochondria. Mitochondria are membrane-bound organelles involved in energy production and are characteristic of eukaryotic cells.
For your second question, the organelle that you would ONLY find in a prokaryotic cell is the nucleoid region. The nucleoid region is where the genetic material (DNA) is located in prokaryotic cells, as they lack a defined nucleus.
To summarize:
- Eukaryotic cell: Mitochondria
- Prokaryotic cell: Nucleoid region