Answer
K+ ions diffuse out of a resting cell due to the concentration gradient across the cell membrane and cell membrane is more permeable to k+ jons than any other ion.
Work Step by Step
In intracellularfluid, along with K+ ions there are many cytoplasmic anions that cannot escape from the cell because Of their size or charge like phosphates,sulfates,small organic acid,proteins etc... Due to outflow of k+ out of cell,the ICF grows more and more negatively charged.As a result,it exerts a stronger attraction for the K+ ions and attracts some of them back into the cell.
