Question

which of the following is only found in eukaryotic cells?
nucleus
dna
cell membrane
ribosomes

Explanation:

To determine which structure is only in eukaryotic cells, we analyze each option:

• DNA: Found in both prokaryotic (e.g., bacteria) and eukaryotic cells (e.g., plants, animals). Prokaryotes have circular DNA in the nucleoid, eukaryotes in the nucleus (and mitochondria/chloroplasts).
• Cell membrane: Present in all cells (prokaryotic and eukaryotic) to regulate substance movement.
• Ribosomes: Both prokaryotic and eukaryotic cells have ribosomes (though prokaryotic ribosomes are smaller, 70S vs. eukaryotic 80S).
• Nucleus: Eukaryotic cells have a membrane - bound nucleus containing genetic material. Prokaryotic cells lack a nucleus (their DNA is in the nucleoid region without a membrane). So the nucleus is unique to eukaryotic cells.

Answer:

A. nucleus