Final answer:
Water is the substance that passes through the cell membrane by osmosis, which is the movement from an area of lower solute concentration to one of higher solute concentration.
Step-by-step explanation:
The substance that passes through the cell membrane through the process of osmosis is water. Osmosis is a type of passive transport that involves the movement of water molecules across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This process is essential for cells to maintain balance with their environment and regulate their internal conditions. Glucose and sodium typically move through facilitated diffusion or active transport mechanisms, involving specific transport proteins, while proteins are generally too large to pass through the cell membrane via osmosis.