Answer : 1. "Nucleus"
Explanation :

Answer: A) Nucleus Explanation: Eukaryotic cells contain membrane-bound organelles, including a nucleus. Eukaryotes can be single-celled or multi-celled, such as you, me, plants, fungi, and insects.   Whereas Prokaryotic cells do not contain a nucleus or any other membrane-bound organelle. Bacteria are an example of prokaryotes.