how does this solution make sense? I thought protons were unable to move?

1. (1 point) In the figure, metal sphere A has 4 negative charge units and metal sphere B has 2 positive charge units. What is the charge state of the spheres after you touch them together? After touching Touch net A. Sphere A and sphere Beach have -2 charge charge charge Sphere A and sphere Bleach C. Sphere A has -2 charge and sphere B has 0 charge D. Sphere A has +2 charge and sphere B has I charge