Final answer:
The structure shared by both prokaryotic and eukaryotic cells is the cell membrane (b). It acts as a barrier for the cell, controlling substance exchange with the environment.
Step-by-step explanation:
The components that all prokaryotic cells and eukaryotic cells share are the plasma membrane, the cytoplasm, ribosomes, and their genetic material (DNA or RNA). Among the options provided, the correct answer is b) Cell membrane. Prokaryotic cells, such as bacteria, and eukaryotic cells, including animal, plant, and fungal cells, both have a cell membrane. This membrane acts as a barrier, controlling the entry and exit of substances. Furthermore, this cell membrane has a similar structure across all forms of life, indicating a common evolutionary origin.
Prokaryotic cells do not have a nucleus or other membrane-bound organelles such as endoplasmic reticulum or mitochondria, which are found exclusively in eukaryotic cells. Therefore, options a), c), and d) are not features shared by both cell types. In contrast, the cell membrane is a fundamental component of all cells, and its function is essential for maintaining the integrity of the cell and facilitating communication and transport between the cell and its external environment.