Eukaryotic cells contain organelle-specific structures

Steps:

• Recall that eukaryotic nuclear DNA is linear, but mitochondrial DNA is circular.
• Note that eukaryotic cytoplasm contains 80S ribosomes for protein synthesis.
• Identify that mitochondria (and chloroplasts in plants) contain 70S ribosomes, similar to prokaryotes.
• Conclude that all three features—circular DNA, 70S ribosomes, and 80S ribosomes—are present in eukaryotic cells.

Why A is correct:

• Eukaryotic cells have circular DNA and 70S ribosomes in mitochondria, plus 80S ribosomes in the cytoplasm, per standard cell biology definitions.

Why the others are wrong:

• B: 70S ribosomes are present in mitochondrial organelles.
• C: Both 70S (mitochondrial) and 80S (cytoplasmic) ribosomes are present.
• D: Circular DNA is present in mitochondria, and 80S ribosomes are in the cytoplasm.

Final answer: A