1. The problem asks to identify the role of the cell membrane in the egg model when placed in different solutions. 2. The egg shells were dissolved to mimic red blood cells, focusing on how the cell membrane interacts with water and solutes. 3. Important concept: The cell membrane is selectively permeable, meaning it allows certain substances like water to pass through but restricts others like many solutes. 4. Observations from the model: - In 5% vinegar (hypertonic solution), the egg shrinks because water leaves the cell. - In pure water (isotonic or hypotonic), the egg remains normal size as water movement is balanced. - In corn syrup (hypertonic), the egg swells or distorts due to water movement. 5. This shows the cell membrane allows water to enter and leave the cell, regulating cell size by osmosis. 6. Therefore, the correct statement is: **The cell membrane allows water to enter and leave the cell.**