Final answer:
The sodium-potassium pump maintains a negative charge inside the neuron by transporting three Na+ ions out for every two K+ ions in, resulting in a net positive charge exiting the cell. This, coupled with the selective permeability for potassium ions, leads to the resting membrane potential in neurons.
Step-by-step explanation:
The component that keeps the charge inside the neuron negative compared to the outside is c) the sodium-potassium pump. This pump actively transports three sodium ions (Na+) out of the cell for every two potassium ions (K+) it brings in, thus generating a net loss of positive charge inside the cell. Additionally, the resting membrane potential is due to not only the action of the sodium-potassium pump but also because potassium ions, which are more concentrated inside the neuron, can move out through potassium channels more freely than sodium ions can move in. Consequently, the departure of K+ ions contributes further to the net negative charge inside the neuron. This electrochemical gradient, maintained by the sodium-potassium pump, is essential for the resting state of the neuron and is crucial for nerve impulse transmission.