Why Do Na⁺ ions Enter the Cell When Voltage- Gated

Why do Na⁺ ions enter the cell when voltage- gated Na⁺ channels are opened in neurons?

A) because the Na⁺ concentration is much higher outside the cell than it is inside
B) because the Na⁺ ions are attracted to the negatively charged interior
C) because the Na⁺ ions are actively transported by the sodium- potassium pump into the cell
D) both A and B
E) both A and C