Final answer:
Both DNA and ribosomes are found in prokaryotic and eukaryotic cells. DNA is located in the nucleoid region of prokaryotes and enclosed in the nucleus of eukaryotes, while ribosomes are responsible for protein synthesis in both types of cells.
Step-by-step explanation:
The structures that are found in both prokaryotic and eukaryotic cells include DNA and ribosomes. DNA is the genetic material of the cell. In prokaryotes, DNA is present in a nucleoid region, whereas in eukaryotes, it is enclosed in a nucleus. Ribosomes, on the other hand, are the sites of protein synthesis found in both prokaryotic and eukaryotic cells. Thus, the correct answer to the student's question is C. both A and B, which means both DNA and ribosomes are found in prokaryotic and eukaryotic cells.