The correct similarity between prokaryotic and eukaryotic cells is:
Both prokaryotic and eukaryotic cells are filled with cytoplasm.
Prokaryotic cells do not have a nucleus or membrane-bound organelles, while eukaryotic cells do. Also, not all prokaryotic and eukaryotic cells have a cell wall. Therefore, the statement about both types of cells being filled with cytoplasm is the only accurate similarity among the options provided.