The correct answer is c. plasma membrane.
The main difference between the prokaryotic and the eukaryotic cell is the presence of nucleus. The eukaryotic cells have nucleus and the prokaryotic cells do not have the nucleus. The nucleolus is present inside the nucleus, in case, the nucleus is missing, nucleolus also does not exist, hence, it is absent in prokaryotes.
Plasma membrane is common in both types of cells, it forms the outer boundary of the cell and keep the cell isolated from atmosphere.
