Final answer:
A cell with a membrane potential of -90 mV would have the greatest electrical attraction for sodium ions to enter, given it is more negative than the other options and thus provides a stronger electrical gradient for positively charged Na+ ions.
Step-by-step explanation:
The electrical attraction for sodium ions to enter a cell is mainly driven by the membrane potential. In cells where this potential is strongly negative, the attraction for positively charged sodium ions (Na+) is greater due to the increased electrical gradient. The more negative the membrane potential, the stronger the drive for Na+ ions to enter the cell to balance the charge.
Given the options, a cell with a membrane potential of -90 mV would have a greater electrical attraction for sodium ions compared to the others. This is because -90 mV represents a more negative internal environment relative to the outside, indicating a stronger electrical gradient for Na+ ions to move into the cell to lessen this difference. Conversely, a potential of 0 mV or +20 mV represents a scenario where the inside of the cell is less negative or even positive relative to the outside, thus decreasing the driving force for Na+ to enter based on electrical attraction alone.
This concept is deeply rooted in the resting membrane potential, typically around -70 mV, which changes during processes like depolarization, where Na+ rushes into the cell, making the inside less negative and ultimately reaching a positive membrane potential during the action potential in nerve cells.