Respuesta :
if sodium entering and exitting the cell is observed, then it is clear that the cytoplasmic membrane is being looked at under the microscope.
Answer:
C. Plasma membrane
Explanation:
Plasma membrane is bilayer of phospholipids in which proteins are embedded. It serves as selectively permeable membrane and regulate the entry and exit of various molecules in and out of the cell. Hence, the observer is looking at the plasma membrane of the prokaryotic cell through which transport of sodium ion is occurring.