Shared Cellular Feature: 70S Ribosomes

Steps:

• Identify prokaryotic cell components: lack nucleus, contain 70S ribosomes, circular DNA in cytoplasm.
• Identify eukaryotic cell components: have nucleus with linear DNA, 80S ribosomes in cytoplasm, but 70S ribosomes in mitochondria and chloroplasts.
• Compare for common elements: 70S ribosomes present in both cell types.
• Eliminate options absent in one or both: centrioles, circular cytoplasmic DNA, and starch granules.

Why A is correct:

• 70S ribosomes are the standard size for protein synthesis in prokaryotes and in eukaryotic organelles like mitochondria, per ribosomal subunit classification.

Why the others are wrong:

• B: Centrioles organize microtubules during division but are absent in prokaryotes and most eukaryotes like plants.
• C: Circular DNA resides freely in prokaryotic cytoplasm but eukaryotic DNA is linear and nucleus-bound.
• D: Starch granules store energy in plant eukaryotic cells but are not found in prokaryotes or animal cells.

Final answer: A