Final answer:
None of the provided options accurately represent the process of reaching equilibrium based on the concentrations of KCl inside and outside of a neuron. Equilibrium is reached through continuous ion exchange to balance electric and chemical gradients, not by a fixed transfer of ions represented by a numerical value.
Step-by-step explanation:
To achieve equilibrium, a neuron cell selectively permeable to potassium with a concentration of 40 mM of KCl outside of the cell and 105 mM of KCl inside the cell will cause potassium ions (K+) to move down their concentration gradient. The movement of K+ ions will be from an area of higher concentration to an area of lower concentration until equilibrium is reached. Considering the neuron's resting membrane potential, potassium ions will move out of the cell, as the inside of the neuron is negatively charged and potassium ions are in higher concentration inside the cell. This leads to a net flux of K+ from inside to outside of the cell.
However, the option which accurately describes this movement and the specific numerical value provided in the multiple choices is not scientifically valid, as equilibrium is not represented by a fixed amount of ion movement but by the continuous dynamic process of ion exchange reaching a balance. Therefore, the net movement will not be quantified as a specific millimolar (mM) value, but it would continue until the electric and chemical gradients are balanced.
Given this understanding, none of the provided options A, B, C, D, or E correctly explains the process to reach equilibrium regarding the movements of K+ in a neuron cell. The numerical values in the options do not correspond with the process of establishing an equilibrium in the context of resting membrane potential in a neuron.