Final answer:
The cell cortex, particularly the actin cortex, contributes to the flexibility and structural integrity of the cell, allowing it to change shape and move, especially important in narrow passages such as capillaries. The cell cortex is not involved in the direct passage of small molecules, nor does it lubricate the cell; its functions are more mechanical and structural.
Step-by-step explanation:
The functions of the cell cortex, specifically the actin cortex underneath the plasma membrane, are critical for maintaining the structural integrity and flexibility of the cell. One of its primary roles is to allow cells to change shape and move, particularly important for cells like red and white blood cells as they pass through narrow capillaries. This function is tied to the flexibility of the membrane and the strengthening of the membrane, as the actin cortex is a dynamic network that contributes to the cell's mechanical properties and can respond to deformation.
The cell cortex does not influence the passage of small molecules directly; that is a function more associated with the plasma membrane itself, which contains channels through the membrane formed by proteins for selective passage of substances. Regarding the options provided, option (b) 'It allows cells to change shape and to move.' best aligns with the function of the cell cortex.