Which of the following structures is present in both prokaryotic and eukaryotic cells?

Chromoplasts are a type of plastid found primarily in plant cells and some algae, responsible for the synthesis and storage of pigments. They are not found in prokaryotic cells or in all eukaryotic cells, making them an exclusive feature of certain eukaryotic organisms. Therefore, they cannot be considered a shared structure across all cell types.

The Golgi apparatus is an organelle involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles. It is a characteristic feature of eukaryotic cells, but it is absent in prokaryotic cells, which lack membrane-bound organelles. Thus, it cannot be counted among structures common to both cell types.

The endoplasmic reticulum (ER) is an extensive membrane system found in eukaryotic cells, playing vital roles in the synthesis of proteins and lipids. However, like the Golgi apparatus, the ER is not present in prokaryotic cells, which lack the complex internal structures found in eukaryotes. Therefore, it is not a universal feature.